I don't think Zetas are as much a problem as omegas are. Every character has omegas to max their abilities. Not every character has a zeta. (Not that you should go and drop a zeta on the few remaining that don't have them CG!)
To max out characters with 2-3 zetas, you need dozens of omega pieces, JUST for the zetas. All the other abilities need omega pieces too. Newer characters require 5 omegas for each of those abilities. (i.e., C3PO needs 51 omega pieces to max everything. 51 for just ONE character)
I can get 2, sometimes 3 zetas worth (20 pieces each) in a month.