Zombies themselves are not overdone. However, you have to have more to a story than "it's about the zombie apocalypse" for anyone to be interested, because that on its own is, quite simply, not a good read. I don't mean to be offensive, it's just the way it is. It's like me telling someone I'm writing a story about a dragon that makes friends with a person. "Oh, yawn, that's only happened a million times before." But what if I tell them that the dragon is actually a secret agent for a pants factory, and the human is a robot who believes that pants ought to be made illegal?
...Okay, not quite like that, but you get the idea. If you're just writing "zombie apocalypse," then you'd better make sure you have some REALLY interesting characters that bring something new to the table. If not, you're going to need some plots within that in order to keep people interested. Maybe one of the characters falls in love with a zombie, or there's some zombie cult that believes being undead is the way of the future.