From the introduction:
Zombies are untiring, fearless waves of mindless destruction. The proverbial horde of zombies shambling toward a village of innocent souls can bring horror to the stoutest of hearts. However... they’re really only dangerous in large numbers because, let’s face it, zombies are slow. But what if a zombie wasn’t slow? What if a zombie moved faster than you, caused multiple wounds, and could evade your attacks even better than when it was alive? The primitive horror of a mass of zombies could quickly turn to true terror from just one zombie.
Walking, climbing, swimming, flying, and burrowing into your homes, included here are 46 fast zombies from CR ½ to CR 11 with multiple attacks to cause even the most stalwart group of adventurers to quail in fear. Fast zombies don’t shamble, they run.