This thread is awesome!
Has anyone seen the episode of Deadliest Warrior with Zombies vs Vampires? The best way to "kill" a zombie is to destroy its brain. This stops the signals from it's brain reaching the rest of it's body. Zombies are like superhumans. They are capable of doing what they do because there isn't anything limiting their bodies. We feel pain to let us know we are pushing our bodies too much. Zombies don't feel pain and are only limited by physical mechanics.