There's an airsoft field in Fremont NH that does occasional nerf wars and is now doing a zombie-themed LARP. Here's their description of it:
NH Boffer Fighting runs The Compound zombie apocalypse Live Action Role Playing (LARP). Based on Nerf blasters with a mixture of boffer and other elements mixed in, The Compound is more battle driven while still having a story at heart. Teams are built around three main groups: the Lifers which include both a Civilian and also a Military team, and the Zombies. Who survives and who thrives depends on teamwork, skill and daring do. The Compound will be held this year on Saturday, June 15, 2013 from 2PM till 10PM. For much more updated info, please be sure to check out the event page on Facebook when it is posted!
are the rules. They're pretty different from normal HvZ rules and I have some reservations about them but it still seems alright.