Why would anyone kill a zombie? They're a GREAT source of unlimited energy! What you do, is you construct (in advanced) a large facility, where electricity is derived from the rotation of this large, thick, bullet proof glass rotor like wheel. On the other side of this rotor is a gaming room with a non-translucent wall opposite the glass wall. You herd the zombies into the chamber with the rotor, and put some people into the gaming room, the zombies will constantly try to get to the gamers by either running into, trying to push aside, or just walking into the glass, pushing it along a circular track within the chamber, thus generating electricity. Have enough of these facilities over the world, and what was going to be a zombie problem, becomes an energy solution! Cause after all, zombies never get tired! Course, if a zombie was to escape, you could just lure it back into the chamber, they don't seem to be too smart. And if you find a smart one, kill it before it organizes the others.