From the release:
RPZ is a Universal Roleplaying Supplement designed to be used with any RPG system. Continuing with Spectrum Games’ niche of genre emulation, RPZ can easily be incorporated into any system to bring some of the cinematic aspects of the zombie genre to your zombie game. Spectrum is not looking to reinvent the wheel; there are plenty of zombie games out there, and every person has a different opinion on what a zombie should be -- fast, slow, intelligent, brain-loving, and many people have already broken this down into game mechanics. Instead, RPZ will bring some of the tension and paranoia prevalent in the zombie genre to your game. Easily implemented, and extremely narrative, RPZ will have players and characters feeling the dread of a world overrun by these undead!