Quote Originally Posted by Kraco View Post
They seem to be powered by human sacrifices. That is, a corpse inside that dirt is giving them energy.
Yes, but when they can get completely obliterated by an attack and still reform from nothing, it's obvious that the state of the corpse inside is no longer relevant once the jutsu has been cast.

It also seems unlikely that the sacrifices chakra is being used to power the jutsu, since the sacrifices are usually total schmucks, but the zombies still have the chakra to perform kage-level techniques.