The Haitian Zombie is all just made-up. It has been de-bunked countless times.
Sure let's inject an unknown substance to create zombies.

I mean the body-snatcher idea is more feasible, despite requiring an appreciation for a supernatural clause.

However, I actually came up with a third-zombie type thinking of this.
Imagine like Cold-War era "sleeper spies". Yeah, once activated they lose their sense of identity and can only function on their objectives. Now imagine if their objective was mass murder in the opposing country, you see where I'm going with this.

In fact, its very probable for such a "zombie".
- People can block out pain via mental state, via a trauma/brain-overload, or via chemicals,
- People can be conditioned to behave more primitive, like an ant or a zombie
- A device hooked to someone's brain could be controlling them


So I give you 3 forms of possible zombies (ranging from most to least likely):

1) Brain-washed person (disposable, primitive thinker and pain blocker).
2) Mentally degraded person due to Infection (something like a rabid-human).
3) Body-snatcher person (alien/demon/supernatural explanation)

Now the question that remains is 40x Green Anacondas versus 50x Silverback Gorillas. FIGHT!