In my opinion they can't have more chakra than the sacrifice provides. Where would anything beyond that come from? Surely not from Kabuto running a hundred zombies at the same time. And certainly not from the mockery of dead spirits the zombies represent. I bet if you kept destroying the body countless times, the regeneration alone would cause the thing to run out of juice and disappear into thin air.

Otherwise the fricking jutsu would be a perpetual motion machine in addition to everything else haxored.