Just completed the 4th challenge level and thereby the Zoo Maker and Water Zoo challenges. They're a bit tricky, but we got them done in a couple of days. For anyone having trouble, feel free to reach out to me, I can tell you the tricks to it.
All in all I don't think the challenges are too hard (maybe the upped spawns in 1.15 fixed the issue? Didn't play SB back then though, so can't compare)
Another issue however: In the Elite level, I suspect two challenges of being unobtainable:
- The Hostile Mob Zoo requires Skeleton, Zombie, Witch, Husk, Enderman, Creeper, Slime, Phantom, Endermite, Magma Cube, Spider, Pigman, Drowned, Blaze, Ghast, Wither Skeleton. I can get all of these mobs, but not in the same dimension, and Sentinel disables mobs from going to portals. (You can change the biomes in the nether (though you can't change them back to nether), but I doubt the nether has slime chunks)
- The Engineer (all redstone components, repeat x100): This is doable once or twice, but it requires 5 pieces of Quartz, which is not renewable. Currently we have 24, fortuned from the nether starter island.
Maybe the first one can be split up into a Nether and Overworld Hostile Zoo, and the second one scaled down from a 100-times repeatable to a once-off?