Not too shabby
Like everybody else says, there is a few things you should fix.
I kind of noticed on the zombies they turn red when hit but maybe a little better registery of them being hit would be good.
Lets see where to start.. I loved the music and the violence was pretty good, I hope in 3 there would be more dead bodies of humans to give it a real gritty zombie like feel, maybe a few more weapons but the ammo being pretty scarce. The only other flaw I can think is to put some wooden fences or objects in certain parts you can't walk (invisible corners). Other than that, its pretty good.