There is a class description file available on the main ACE site. It does have gaps though. The devs know about that and are hoping to come up with a way to automate the generation of this file during the mod build so it is more complete, up-to-date.
You could park an ammo truck near the ZU to resupply it, would be quite realistic that way.
If neither of those work, let me know and I'll dig for ya. :)