you can buy it using real money (boo hiss) - at the charge zen link at the top of the forum - or when in game you can trade for it with Dilithium - next to the mini map is a down arrow, first option is the Dil exchange
In total, I ended up with about a grand total of 2k Zen, gained in periodic transactions throughout December. I have yet to buy anymore this month, due to my dilithium having gone toward the Hyper Plasma Torpedo, the Omega Plasma Torpedo, and now going to an Elite Fleet Sniper Rifle. After I get that rifle, I do hope to start saving up dilithium again so I can be buying more Zen.
I've exchanged dil for around 3000 Zen so far, got myself a free ship, but I don't think I will do much more of that as I've now got everything I want from the C-Store and need the dil for dil things more.
I love the Dil:Zen being so low, I got 10k zen so far here. I bought the Vesta bundle for 5k and besides that there isn't much I want to buy but with news of several ships to be released early this year I decided now would be a good time to save more Zen. By Sunday I should be able to buy another 5k to bring my standing balance to about 11k.
So I say to all those with more money that sense or those who have too much money to care, keep pumping Zen into the economy.
You know I am one of thoe pumping Zen into the economy but with threads like this and the ones about the crashing Dil market. I think I am gonna refrian from a while since I have far more Zen(bought with real world cash) than I do Dil, since it seems I am upside down profit wise in this current marketplace.
I haven't really been farming dil (winter wonderland and doing Foundry missions mostly), so only about 1.5-2K, and that's pouring all my dil to the exchange. Along with $20 of zen, I got +100 doff slots for all my toons, and some keys to try some of the old boxes with the reruns, since I missed the Ferengi and Tholian ones.