The trails lie on a tilted layer of Shinarump conglomerate. Bloomington Hill angles upward from northeast to southwest. These trails lie on the northwest side of the cliffs. Below the cliffs is the valley containing the Bearclaw Poppy area trails.
There are no "easy" rides here. All except the Siler Loop should be considered expert. Intermediates who want to ride here should climb the Powerline Road to Siler Bluff road and ride the Siler Loop. Then pick among various trails in the downhill direction -- planning to make a few walk-overs as you go.

In describing these trails, I will refer to the trail from the Zen loop over to the Siler Bluff road as "Mega Zen." It will be divided into two segments: an upper one-way high-expert DH section from Zen to the Powerline Road, and an upper-intermediate section from Powerline to Siler Road.
The term "Mega Zen" can also refer to the of Zen that combines Mega Zen with some combination of the lower trails plus dirt roads that link back to Zen. So the Bloomington Rim trail can also be considered part of Mega Zen.

Bad weather / low-clearance sedan parking
On Tonaquint Drive between Dixie Drive and Bloomington Drive, turn west on Curly Hollow Drive. Go past the school and continue to the end of the pavement. Start the ride by pedaling up the dirt road. Follow the directions below.

Bloomington Hill Trust Land trailhead
At pavement's end on Curly Hollow Drive, the dirt road turns left. It will pass a race staging area as it climbs a low hill. After cresting the hill, keep straight as the Curly Hollow doubletrack forks to the right. Descend past the fenced power station property and turn left. Drop into the washbottom, then turn to the right and begin to go uphill on the main dirt road. About 50 feet from the bottom of the wash, fork right into a parking area. Begin the ride by climbing the Powerline Road. Alternates: The Wash Trail is on the left 50 feet uphill from the parking entrance. After 100 yards on the Wash trail, the Bloomington Rim trail will fork to the right uphill.

Via the Zen Trail
From the Green Valley competition area, start uphill on Zen riding counterclockwise. At mile 2.9, as you ride east-southeast along the edge of the cliffs, the Zen trail will curve to the left away from the edge. A less-obvious trail continues straight here, dropping steeply down through a technical area. This is upper Mega Zen, a high-expert (double-black) downhill-only trail that will take you to the rest of the trail system. This trail has significant exposure to cliffs and is extremely technical.

Bloomington Hill is formed from a tilted layer of Shinarump conglomerate overlying the clays and sandstone layers of the Chinle formation. The rock starts out level with the valley but tilts up so that as the cliffs break away down toward the Bearclaw Poppy area, 300 feet of elevation has been gained.

Compared to the layers underneath it, the Shinarump tends to resist eroding away. As water attacks the surface, it breaks down into slabs, nuggets, and domes. In crevices and soil between "bumps" of rock, brittle sage, ephedra and cactus grow.
While some areas have smooth rock, mounds and ledges are common. This creates the riding challenges that expert riders want. But it's a lot of work. Except for the Siler Loop, the trails here are expert-level in the either direction, with a dash of extra challenge when heading uphill.

With no trees to block the view, you'll be able to enjoy open views in many directions. To the north are the Pine Valley Mountains. Northwest are the red Navajo sandstone cliffs of Snow Canyon. You'll be able to spot the mesas to the east past Bloomington.

On the trails below Mega Zen, navigation and route-finding can be tricky. There are no trail signs and no paint spots. Even on weekends, it's unlikely that you'll find another biker to ask directions. An occasional out-of-place rock may be the only marker of the trail. For a first-time ride, it's significantly easier to find your way when riding top-to-bottom. And if you have a specific route in mind, use a navigation aid such as Trailforks.

Mega Zen (called "The Art of Motorcycle Maintenance" after the book "Zen and The Art of Motorcycle Maintenance" by the trailbuilders) is 1.5 miles in length, extending from the Zen trail loop east to the Siler doubletrack near the Siler Loop. It includes an upper one-way DH portion and an easier two-way segment. The upper half of Mega Zen is rated "double-black." Only confident true experts should ride this trail!

The upper section of Mega Zen is 0.8 miles long, with 300 feet of elevation loss. There's only a little bit of climbing, but it's sudden and steep. This portion of Mega Zen is a highly technical and challenging trail with exposure to steep side-slopes and cliffs.

Upper Mega Zen forks away from the counterclockwise Zen loop as Zen turns away from the cliffs to begin descending north. Compared to Zen, the Mega Zen trail is relatively narrow and faint. So you'll need to be watching for it.
The descent begins with steep winding trail through the sandstone. You'll drop 100 vertical feet in 1/10th mile. The route will then level out, although the degree of challenge remains high. Mega Zen has quite a few expert-level rock challenges, with wooden ramps for some bigger rocks.

After a half mile on top of the hill, the trail dips down below the upper cliff line. Here Mega Zen runs along a steep side-slope in the Chinle formation clay just below the Shinarump caprock and just above a second set of cliffs. There will be some up-and-down and a bit of rock-dodging.

At the eastern end of upper Mega Zen, the trail will drop steeply. Once again, you'll lose about 100 feet of elevation in 1/10th mile. And the drop-off is never far away.

Just before the doubletrack turns at the power poles, the singletrack cuts across to the left of the road. After joining the road for a few feet at the bottom of the dip, it will climb through several switchbacks to get up above the road again.
The trail now drops down and across the Powerline road. If you're done, simply turn left and head downhill on the road. For (a lot) more work, veer downhill across the road to enter the lower segment of Mega Zen. This will take you to the Bloomington Rim trails for more tech riding as you descend.

The next section of Mega Zen is 0.7 miles. The trail now becomes two-way. There will be around 100 feet of climbing and 200 feet of descending as the trail continues east. You're away from the cliffs and riding across the slope of the hill.

This portion of Mega Zen would rank upper-intermediate overall, with a short bit of expert-level rock on each end. There are some long stretches of simple pedaling but also periodic rock challenges that require good skills.

The trail winds through brittle sage and ephedra. The long non-technical stretch in the middle of this segment is a welcome respite.
Around 1/10th mile in, a sketchy trail comes from downhill on your left. You may not see it. This trail heads out to the Powerline road. Keep right and eastbound.

As the trail approaches the Siler Bluff dirt road at mile 1.5 from Zen, it will drop through some challenging rock. If you keep turning to the left after the initial drop, you'll find the top segment of the Bloomington Rim trail on the left. (You'll turn a total of 180 degrees.) This is the way to go if you're doing Mega Zen without the Siler Loop.
If you point the bike down the second set of steep rock ramps, you'll reach the Siler Bluff road, where a right turn will take you to the Siler singletrack loop. A left turn on Siler Road is the quick way downhill if you're going to bail on further tech riding.

The Bloomington Rim trail is a series of trail segments that descend 2.1 miles from the bottom of Mega Zen to the Wash trail at the Bloomington Hill trailhead. These are two-way trails, but have significant expert-level challenges and tough climbing whichever direction you go.

For simplicity of navigation, I'll describe a continuous route that keeps to the right at the trail forks from this point downhill. That seems to be where most riders are going.
While these are two-way trails, the layout and the "sight clues" seem designed for a downhill ride. If you choose to climb them on your first time here, expect to spend a bit of time looking for the continuing trail, blowing past trail forks, and squinting at Trailforks on your phone. By comparison I had only rare moments of "Dude Where's My Trail?" during the descent.

The top segment is 0.3 miles long. Here the Bloomington Rim and Bloomington Hill trails are combined. This section extends from the bottom of Mega Zen to the first trail fork.
At this fork, a right turn takes you on a meander referred to as Bloomington Rim South or Upper Bloomington Rim, while left puts you on a shorter alternate descent via the Bloomington Hill trail that will bypass the meander.

The upper Bloomington Hill alternate trail forks away from Bloomington Rim at mile 0.3 from Mega Zen. It's a faster way down than the upper meander of Bloomington Rim (see below). The trail fork occurs just as the upper descending trail makes a curve downhill to the right, and it's easily overlooked. If you see the Silar Road ahead, you went past the trail fork.
There will be a faint trail on the left about half-way down this section. This will take you out to the Powerline road. Keep right and descend toward Siler Road.

This section of Bloomington Hill is 0.3 miles long, as it will rejoin Bloomington Rim at the Siler Bluff doubletrack.
At the Siler DT, Bloomington Hill joins the doubletrack northbound. At the same spot, the lower limb of upper Bloomington Rim comes in on the opposite side of the road. Keep straight onto the dirt road and find the continuing singletrack trail veering to the right. The Bloomington Hill and and Bloomington Rim trails will now be combined for 1/10th mile.

The upper meander of Bloomington Rim begins at a trail fork 0.3 miles downhill from the bottom of Mega Zen. Go to the right for 1/10th mile and cross the Siler Bluff dirt road. You'll enter an area of rolling nugget sandstone. Things get a bit bumpy here!

At the eastern end of the meander, there's a stretch of fairly easy singletrack trail. But it's short. Enjoy it while you can.

The route will turn back to westbound and begin dropping into a rocky wash. There's some very technical rock here. You may need to take a scouting look, then back up and make your run.

Once you're in the washbottom, the trail continues west on a gentle climb. When you reach the Siler Bluff dirt road at mile 0.9 from the top, veer to the right onto the road, then right again on the continuing singletrack trail. (If you notice a trail joining on the left side of the road, that's the Bloomington Hill trail. The two trails now join for the next 1/10th mile.)

The Bloomington Hill and Rim trails are joined for 1/10th mile during a climb from Siler Bluff Road to the top of a low hill. Then the Rim trail will fork to the right, while the Bloomington Hill trail goes left. If you turn left downhill on Bloomington Hill (bypassing the 0.7 miles of Bloomington Rim's lower meander), it will be 0.3 miles to rejoin the Rim trail.

After 1/10th mile on the combined Bloomington Rim/Bloomington Hill trail (mile 1.0 from the bottom of Mega Zen via Bloomington Rim), keep to the right at a trail fork. The fainter trail to the left is the Bloomington Hill trail. (If you decide to go left, you'll rejoin the Rim trail after 0.3 miles.)

This section of Bloomington Rim is 0.7 miles long. It will curve out to the east twice before returning to join the Bloomington Hill trail on the eastern side of a shallow wash. Look for cairns above the wash to mark the cross-over spot. At the shallow wash, you're at mile 1.7 of the descent on Bloomington Rim.
It's likely you won't even see the Bloomington Hill trail coming in to join Bloomington Rim. The junction is about 30 feet east of the wash. This piece of the Hill trail can be hard to find even when you know exactly where it is. You could, for example, turn left and use Bloomington Hill as an uphill route to do a second lap of the lower Bloomington Rim meander.

If you're climbing uphill from the bottom segment and want to ride Bloomington Hill instead of the lower Bloomington Rim meander, pedal until you can see a couple of cairns marking the wash crossing. On the east side of the wash, just past the marker rocks, work your way to the right and find a path along the eastern side of the wash going uphill. It will be 0.3 miles to where Bloomington Hill and Bloomington Rim rejoin. (Note that when climbing, Bloomington Rim turns to the left and gently downhill after crossing the wash, while Bloomington Hill turns right uphill.)

Back to the descending route. We're now at mile 1.7 from the bottom of Mega Zen.
After crossing the little wash, veer right and downhill on a long rock ramp. You're now on the final section of the descent. Navigation should be easier now. When in doubt, aim the bike downhill.

This bottom segment is 0.4 miles long, and will include the short connection up the Bloomington wash to the trailhead.
As you approach the wash, the rock challenges will get steeper. (I found some sections of this trail to be non-rideable in the uphill direction.) Again, there's a spot where you may have to look around a bit to find the continuing trail. The navigation problems will get better as more people ride the trail.

As the trail drops into the wash, veer left uphill and pedal to the Powerline Road.
To connect to the bottom of Zen for the "Mega Zen" ride, pedal north out of the wash on the dirt road. Keep left at the road fork (instead of retracing the drive in). There will be two connectors to lower Zen, both on the left. One comes at mile 0.4 and connects to Zen above the sharp drop into the final wash. The second is at mile 0.6 at the fence. Pedal up into the wash and watch for the trail to your right.

The Siler singletrack loop lies on Siler Bluff overlooking northwest Bloomington. The loop is an easier-intermediate singletrack. It's the easiest trail on the hill but overall, the ride isn't really suitable for true beginners, as the dirt-road climb to the loop is tough. And there's one section of technical rock to get past, right at the loop fork.

The loop itself is 1.1 miles of singletrack. It can be reached either via singletrack (lower Mega Zen in the downhill direction or the top segment of Bloomington Rim going uphill) or by a dirt-and-rock jeep road.
The Siler Bluff road forks to the left from the Powerline Road at mile 0.6 uphill from the Bloomington Hill trailhead. (The climb, in my opinion, is too steep for most beginners.) The Siler Bluff Road then extends 0.7 miles south from the Powerline Road to the loop.

When arriving via Mega Zen or Bloomington Rim, fork to the right downhill on the dirt road. Pedal 0.2 miles. As the road makes a hard right turn to climb steeply to a viewpoint, keep straight and find the singletrack fork.

There's one short expert-level section, right at the start of the loop. Less-skilled riders should simply hike their bike up this section, then start the loop in the counterclockwise direction.
Take your time and enjoy the views. There about 150 feet of climbing as you go around the loop.

Just uphill and across the road from the trailhead entrance, a doubletrack trail heads east toward Bloomington. If you stay on the right side of the wash (or in the washbottom), it will take you to Tonaquint Drive in just over one mile.

Getting there:
On Tonaquint Drive between Dixie Drive and Bloomington Drive, turn west on Curly Hollow Drive. Go past the school and continue to the end of the pavement. At pavement's end on Curly Hollow Drive, the dirt road turns left. It will pass a race staging area as it climbs a low hill. After cresting the hill, keep straight as the Curly Hollow doubletrack forks to the right. Descend past the fenced power station property and turn left. Drop into the washbottom, then veer to the right as you climb. About 50 feet from the bottom of the wash, fork right into a parking area. Begin the ride by climbing the Powerline Road. Alternates: The Wash Trail is on the left 50 feet uphill from the parking entrance. In 100 yards, the Bloomington Rim trail will fork to the right uphill.