I tried to save zen by making a fleet specifically to hold my excess stuff that either doesn't bind or hasn't been bound yet.
Ugh, annoyed at myself. Talked myself into opening a couple Temporal lockboxes, thinking that the trend from the Tholian set was to at least give better rewards, right? Well, opened 4 of them, and got:
I'm saving up my dilithium and by the end if November I'm converting it to zen and then I'm buying 50 keys. Mostly to get 200 Lobis for the timeship console, since I know I'll get nothing else of worth.
I'm still rather surprised at the amount of EC I've manage to generate. In the last two weeks I've managed to generate 240m EC, much of which was done by selling everything I have :P and converting all my borg drops into dilithium (then zen, then to items to sell on the exchange).
Fleet modules - sold on the exchange (since the ships I want are T5 shipyard, I won't need them for a while... if ever).
Borg/Breen/Jem'Hadar set equipment - sold (100,000 EC each)
Loads of purple doffs - sold (to be honest, I'm happy to be rid of my 3 useless purple chefs).
Tour the Universe - Gawd I hate the ESD loading bug.
Numerous other things.
Of course now I'm down to 1m EC. Still, I learned a number of quick ways to grind EC.
So all my banks are pretty empty now. On the bright side, it's meant I've gotten rid of stuff I'd have never used anyway.