Apart from The Mummy, I find zombies to be the most ridiculous monsters. I realise the new series (ain't seen it) may portray them as much more mobile, but in any zombie film I've seen, they merely tend to shuffle around.
I've also never figured out what brings them back from the dead. Nor how they got out of their coffins under a ton of earth, some weeks after they've been interred, nor (bearing in mind the phenomenal strength required to achieve their resurrection) how they subsequently can only shuffle about. Maybe they're puffed out.