I am posting this in the off topic forum since the game's c-store is not live. There is currently a sale on ZEN from Perfect World. You get 15% extra ZEN when you purchase through PayPal, Skrill/Moneybookers, ClickandBuy, Google Checkout, or Steam.
Bonus ZEN Begins: Tuesday, February 26, 2013 (at 3:00PM PDT, 6:00PM EDT)
Bonus ZEN Ends: Friday, March 1, 2013 (at 3:00PM PDT, 6:00PM EDT)
Details can be found
here. Read carefully to understand wich payment methods are eligible and note the limitations on purchases through Steam and Google Checkout.
It is possible to save these ZEN for use when Neverwinter officially launches. When you purchase ZEN it goes into a virtual wallet. You can then transfer ZEN from your wallet to any of the various PWE games. Neverwinter is not currently a choice in the games dropdown on the transfer page. It will probably not be until the game launches and the Neverwinter C-Store is live. If it shows up before then I would avoid transferring ZEN to Neverwinter until the C-Store is announced as live.
Beware: Once you have transferred ZEN to a game it cannot be transferred back out for use in a different game or to move to a different server!
I have personally left ZEN in my wallet for months and can confirm that it does not expire. You can also transfer a portion of your ZEN balance at a time, so you can split it between games. If you have confidence as I do that you will indeed be playing Neverwinter at launch then this is a nice way to score a few extra ZEN. If you are unsure or expect long launch delays then you should probably wait and skip this sale.
You can purchase ZEN here:
https://billing.perfectworld.com/charge