I think your book is really good so far. As for something to fix, I'm not the best writer but I think adding some sort of twist would make the story a bit more interesting. Like maybe the zombies can only attack you if you're scared or something else of that nature. I'm not really into zombies but they can be cool, so I'm probably not the best person to ask for advice but here it is anyway, so yeah. Buh-byeeeee ❤️
P.S. keep up the good work