ok its good for start but learn the basics about scriping before you make it. in your script it suppose to have if before not actor dead read tutorials
To make the bodies dissapear, you need to add a kill check like this:
:ZOMBIE_1
if
Actor.Dead(1@) // just replace the 1@ with the zombie variable.
jf @ZOMBIE_1
Actor.Dead(2@) // Do the same as the first.
jf @ZOMBIE_1
jump @ZOMBIE_2
:ZOMBIE_2
Actor.Destroywithfade(1@)
Actor.Destroywithfade(2@)
jump @ZOMBIE_0 // or whatever the first threads name is.