Taking a cue from the Walking Dead... Add a "Gut Zombie" option to zombie manu when they are dead, akin to the one animals have... if you are holding a hunting knife. After you gut them, various quantity of "Zombie Guts" appear on the corpse. If you use the zombie guts, it's lowers the detection radius that zombies will aggro you. So you can get closer without being attacked in some circumstances. Potential scenario: There's 18 zombies crawling around a deerstand (Which seems normal now). You stalk one out of range of the others, kill it, gut it, smear the guts on yourself... then sneak into the deerstand with less chance of aggro.