With respect - Max Brooks may not know what he's talking about, but are you saying that you do? Dude's talking about a fictional zombie apocalypse. Nobody knows if what he's saying is true or not.

Yes, he uses outdated military tactics, and yes, he causes a contrived string of coincidences to make his story happen. This is a tactic that can also be seen in 99% of all stories ever. If the story was, "something happened exactly as expected and the results were in no way surprising" then it'd be a pretty lousy story, wouldn't it?
He takes artistic license. And yes, he runs with it further than he probably ought to. But so what? It makes for a fun story, and at least he does a better job of making it "real" than the 99% I mentioned above. He's made an effort, as opposed to Roland Emerich justifying the end of the world in 2012 because "The Neutrinos have mutated and they're heating up the planet!"
Max Brooks is attempting to justify a fictional, physically impossible phenomenon, and then stretch that into a global apocalypse, and we're splitting hairs because his fictional biology lesson isn't fictional enough?

Look, if you don't like the story, then that's fine; I respect that, and you as well. Nobody's saying you have to. But at this point in the conversation, this is like walking into a thread about whether Batman or Iron Man would win in a fight, and informing everyone that You guys are talking about fictional characters, this is pointless? Didn't you know they're not real? Of course we know that, but that doesn't mean the story isn't fun.
Essentially, I'm saying don't be that guy. You don't wanna be that guy. If you didn't like World War Z or thought it was badly done, that's fine; I just disagree.