Best way to farm zetas????

Start working now on a good fleet for the future. Ship metas tend to change slowly, because the devs have only put in token effort for them. Even though it's likely that there will be a meta shift by the time you're ready, an Ackbar, Falcon, Hounds tooth, Phoenix fleet will likely boost you up quite a bit. Especially if you go hard after it now at a very early stage. It will be a looooooooong time before you see a payoff in better fleet rewards, but there are no fast solutions in this game. Even spending is meaningless due to how badly overpriced everything is. You have to dump thousands in very strategically to make any significant progress in the short term. Speaking of long term, do NOT spend fleet currency on anything but building your fleet to max, and can max the Zeta challenge. Buying Zetas with it early is cutting your own throat.