I love this. A great deal. Everybody loves Zompocalypse. Not to mention, the Zombie Survival Guide by Max Brooks provides a metric crap-ton of Anti-Zombie defense, and actually advises the use of middle-age armor versus zombies - guess what, you're already there! I honestly think you should look into this book. Even if some of the things happen to be 20th century, there's still enough generally applicable material that you might want to include some of it into the campaign - or, better yet, let the players. If you allow them to research zombies and such, let them find accounts of towns being ransacked by zombies and how the survivors fought them off and...well, survived. Use sparingly though, as too much knowledge at once might make the PCs invincible: the ZSG didn't plan for magic, after all.