Ooh, yes, this would be cool. Although the thought of poisoning zombies who are already dead in a certain way and probably are poisonous themselves is somewhat weird.
Then again, they do move, so they do have some kind of a nervous system, with neurotransmitters and everything. So a paralytic poison such as curare would be effective and probably even incapacitate them to a point where you don’t have to pulp them – if they do come alive again, they’re still inanimate so not really dangerous.
Yeah, poison arrows definitely would be fun, probably posing dilemas like “you can take down the thing faster but can’t use any meat from it”. Like, making mutagen from poisoned tainted meat would not be an option.