It wouldn’t take much to get them started fighting.
It wouldn’s surprise me (too much) to learn that Zero is trying to do just that.
It wouldn’t take much to keep them fighting, recruiting jihadists from all over the world (particularly the young nimrods) into multiple competing gangs, er, militia groups. Make sure none of them acquire a decisive edge, or run out of ammo, and let them feed themselves to each other’s guns.
It would surprise me a lot if zer0 is not on the side of the most radical of moose limbs.