This is probably not going to be the best review as I can't for the life of me remember how this ended from the top of my head. Probably some cliff-hanger like the rest of the books in the series. This is the fourth book in the series so if you haven't read any of them why not go check out my reviews of them: Zom-B, Zom-B: Undergound and Zom-B: City.
We get more explanations here and I'm not at all impressed with them. I did go "really" a lot and laughed at once at the absurdity of it all. I know this written for kids younger than me, but they do have brains (the zombies haven't got to them yet). I guess most won't realise what a staple in horror the explanation turns out to be. Probably just think of Call of Duty, but there is literally films out there about this from at least the 60s.
I gave this book 3 out of 5 stars for Nazi Zombies. I'm just not loving this series at the moment. I've got the next book in the series to read which I'm going straight on to now. It's not at the point where I would stop reading but if it gets any worse. Maybe.