gernade or rpg lol to do rpg
have the launcher do its thing and have a ball or rocket have a not showing smoke object on it,
when the ball hits the ground
then
do together
ball is showing false
smoke is showing true

have the smoke have a fire texture, and to kill zombies
if fire is within ??(idk what value will work) from zombie(all of them)
then
w/e kills zombies