Zolo is one of 6 troll mini-bosses that must be killed in order to remove the force field around Jammal'an the Prophet in The Temple of Atal'Hakkar. He can be found on the Northwest platform around the circle.

Zolo casts totems that summon waves of skeletons that can be difficult to deal with. If you can target the totems fast enough and take them out (druid swipe or have a rogue on the lookout) this can be manageable. Note that the skeletons despawn when you kill Zolo so if your party has enough health and you can keep them from going after the healer you can probably just ignore them. You just want to be aware that they're going to appear if you don't knock the totems out fast enough.

He also drops one of the two Green Voodoo Feathers needed for the Warrior, Warlock, Shaman, and Alliance Paladin Level 50 quests.