Found this info in the bottom of the buffs where all the good info is, might help with this as well to do something similar to CZDM
DismemberChance, ; decapitation, 0-1; tags are "head,arm,leg" <property name="DismemberMultiplierHead" value="1"/> These zombie properties multiply the set dismember chance. <property name="DismemberMultiplierArms" value="1"/> <property name="DismemberMultiplierLegs" value="1"/>
Also the body damage in CZDM is done by targeting not the head so isn't really using a "body" tag per say. You can also target specific things like arms and legs instead, CZDM just counts anything not a headshot as a body shot with the way it is setup.