Since 1 February 2011, armoured zombies can no longer be reached by going through the Wilderness. Instead, one must get Hartwin to teleport him or her to a safe version of the wilderness, where armoured zombies can be fought by going down the trapdoor to the Chaos Temple Dungeon. As of March 2016 if you are taken there by Hartwin the zombies aren't aggressive and it counts as wilderness again.
Armoured zombies are encountered in Varrock during the Defender of Varrock quest, but these only give 10 experience per kill and have no drops. They do leave behind a "red mist". During the Defender of Varrock quest, this "red mist" must be captured in bottles, making Bottle of mist, used to open doors further into the dungeon, and after this quest they have no use.
Armoured zombies can be found on the first floor of New Varrock palace in Dimension of Disaster, these drop red mist like the ones in Defender of Varrock. This mist can be gathered in regular vials however.
As armoured zombies are classed as undead creatures, a salve amulet/(e) is useful for fighting them. The amulet can also be used alongside a full slayer helmet or its components.
Due to the convenience of an altar above the location of armoured zombies, combat-boosting prayers such as Turmoil, Leech curses, Chivalry or Piety may be used to increase the experience yield.
To maximize profits when killing these zombies, players should pick up most of the stackable/noted drops which include charms, types of planks, pure essence and Blood Runes, but not mithril arrows or eyes of newt. For maximum experience per hour, players should not bury bones (unless using a Bonecrusher) or bother with herbs (unless using Herbicide), but may pick up the valuable herbs and other worthy drops like key halves (rare).