Spear Main + Tarkan + Vampire.
Sometimes the NPC's HP goes dangerously low that having a healer as insurance would be nice. So why not take the Vampire since not only can she tank much better than a staff merc but can also kill 2 mobs at a time.
Spear Main + Sheriff + Hwarang.
Attila is probably the best merc to have for all Zulu TBSs, but my alt has none so I had to use my usual TBS mercs before Zulu was added, Hwarang and Sheriff. Their ranged attacks work well for clearing spider webs in this mission at least.