Zetas For First Order Team

You'll definitely want both of ukr's zetas. Probably og pilot's zeta. Sith trooper is not really that necessary as it gives you a bonus vengence blast on ally death. Boundless ambition is a great zeta in general and will help against certain teams but not really the slkr event. You don't need phasmas zeta as you don't use her as lead. Stormtrooper's zeta is good and there is a variation strategy on tier 1 & 2 that you use him for. OG Kylos zeta is not required for the event but is good later when you throw him with cal.

I haven't personally done the event without any zetas.