I love zombie games, but I am generally not a fan of those that are particularly complicated. I was hoping this would be a zombie defense game or something. It turned out to be actually fairly enjoyable. It's mostly because it doesn't require a lot of thought into it. Granted, I've only gotten into the normal part of the difficulty. I think the graphics are done pretty well. My favorite bit is how funny the zombies look when they're attacking a city.
I appreciate you looking for originality in your games, as this seemed like it. There's a lot going on, but take your time to get used to everything. The detail could probably be a bit better. That would actually be a cool name for a film company. You simply can't get enough zombies!