im wondering why this isnt working (it would be great if someone had some tips or could fix this)

[TheDragonsHeart]

Every 60 seconds:
    trigger:
    summon zombie at location 61, 159, -13 in world “plotworld”
    equip last spawned zombie with diamond chestplate of protection 1
    equip last spawned zombie with diamond leggings of protection 1
    equip last spawned zombie with diamond boots of protection 1
    set last spawned zombie's held item to iron sword of sharpness 
    set max health of last spawned mob to 30
    set health of last spawned entity to 30
    set {_mhp} to maximum health of last spawned entity
    set {_hp} to health of last spawned entity
    set display name of last spawned mob to "&6&lZombie Knight &a%{_hp}%&f/&a%{_mhp}%"
 
on damage of zombie:
  if display name of victim contains "&6&lZombie Knight ":
    set {_hp} to health of victim
    set {_mhp} to maximum health of victim
    set display name of victim to "&6&lZombie Knight &a%{_hp}%&f/&a%{_mhp}%"
on death:
    if name of victim contains "&6&lZombie Knight ":
        cancel drops
        give attacker cookie named "&b&l{&e&lC&a&lo&c&lo&6&lk&3&li&d&le&b&l]"