It's great that ZDoom went to lengths to support the quirky BOUNCES flag from MBF. However, there might be a few compatibility problems left.
The one I'm noticing now is about monsters with FLOAT|BOUNCES, who are expected to raise, fall, bounce & raise, fall, until they gain enough mechanical energy to bounce to the height they need. In ZDoom this behavior does work, but often the monsters manage to jump so fast that they don't hit the floor any more, apparently beating the gravity. In MBF this won't happen -- they'll always fall back to the floor only to bounce back, even with the DROPOFF bounce booster.
You can try the following BEX patch in Doom 1 E4M3 (or any vertical map with lots of imps and such) with ZDoom and then with WinMBF, Eternity (preferably) or maybe PrBoom+. You'll see that in ZDoom the imps will likely fight the lost souls, and often remain moving in air, as if they had NOGRAVITY|FLOAT.
The BEX patch is below.