What is the fastest path to zetas?

I'm going for the tier 3 ship ability mat challenge myself, and to get the 5* tarkin I am planning on going for TIE, FO TIE, Geo Solider, Sun Fac and Geo Spy. These five commonly appear in the fleet shipments as well as galactic war, and the characters to pilot them are readily available. Of course if you have slave 1 farmed or managed to unlock Vaders TIE, then you can cut one or two off this list ( or if you farmed maul and his ship already). Then it's simply a matter of levelling those 5 and three light side ships (ones that are easy to farm, or u wing since everyone got blueprints for it for free), and then boom you can start farming zetas.

I'm also going to point out that the tier 3 ship ability material challenge seems to be the only place you can farm (or maybe even get at all) the ship ability material mk 3.