C3P0 7 stars

Your Ewoks are strong enough. They probably need more speed though. The key here is that under Chirpa lead, all of their basics generate 20% TM. And Elder is even more key because his basic generates additional TM for himself and his allies.
So make Elder as fast as you can, and prioritize him as the target of all your assist calls. Logray has high base speed and has a TM generating move for his whole team so he should be the fastest. Paploo gets a significant 25% speed bonus when he's not taunting which is important because he also calls an assist, so it pays to make him speedy too. Wicket is your damage weapon so mod for offense and speed. Chirpa gets whatever speed you have left.
I did it with the first five of these guys. There is hope.
https://i.imgur.com/jED7XQP.png

Much better team than what I did it with. 2 things: remod for better speed and keep trying! RNG fest!

Took me 8 hours worth of attempts on the final tier with G11 zChirp, G12 Elder, G11 Paploo, G10 Logray, and G10 Scout

I didn’t even have Chirp’s or Elder’s basics Omega’ed and didn’t have Paploo’s diversion ability Omega’ed. Just the one Zeta on Chirp’s lead.

The only one I’d even consider putting more gear on is Elder. If he survives, he can keep reviving!

This is a good team. I finished the event when it first ran using this same team with all zetas, all g11. Speed is over hyped in this event, my highest speed was under 200. Properly modded (for their strengths, not speed) they can do this just fine. It to me less than a dozen attempts. If elder dies try again, other than that, stealth Paploo any time you have the chance, he’ll taunt and gain back protection. TLDR speed overrated, and stealth Paploo.

Whatever floats your boat.

OP has the zetas and the gear. If it's not working, more speed is the cure.

This is what I've done.

I've farmed Health Mods. Every Ewok gets a +30 speed Arrow, and a +10 or higher speed secondary mod in every single slot. It's not hard to farm, and easy to acquire. You are more than geared. Just fix your mods.

When doing the battle, always cloak Elder with Wicket's Special. If Elder dies, redo the event. Keep Elder cloaked as much as possible. Use Elder Revive when an Ewok dies, keep the buffs up, clear any debuffs.

Kill order matters, make sure you remove taunt from the resistance tank, focus fire Chewie, then Hans, Tank, Leia, and the final 2 droids.

It's all based on RNG too, so it will take a few refresh before you get the perfect run.