What do all zombies have in common?
They're dead.
Yes.
They are rotten and unwholesome.
I suppose that depends on if you're a zombie or not.
They're not real.
This is entirely debatable given many work cultures and/or individual motivation levels.
The answer is...zombies never, ever stop.
What might a world be like filled with unstoppable killing machines?
It might not be so bad.
And not just for the zombies.