so you must make a death zone for every 1 and set a location to dont let air units pass there !OR!:
make another location (like in zerling blood when you create heros)
here are the triggers
CONDTION
Current player sends at least 1 zerling to revive unit
ACTION
move all any units owned by current player at death zone to 'Move unit to player'
Preserve trigger
Youll move them to the zone where you send to every player, but they are still invencible
CONDITION
Curren player command at least 1 zerling Movw unit to player
ACTION
remove 1 zerling at the location create one zerling at spawer for current player.
preserve trigger
or you could just remove invincibility ( i dunno wheres that trigger but its on rp's)