This is a good idea, adding more items will decrease zc, as long as those items aren't tradeable. What if zc was cut off from production indefinitely, and the new currency is exchangeable 3:1, so you pay 3 zc for 1 zc, BUT you are still able to trade with the new currency, and items are now payed for with gc at that same 3:1 rate, along with the newly created items? This would quickly drain zc, allowing the demand for zc AND gc to go up, creating more competition, making things much cheaper. That is, until zc goes out, and gc would now dominate in a stabilized manner that won't go out of control like zc did.

This is a twist to my other proposal, which likely would not cause much havoc. Unless you're a butthurt business man who doesn't know the first thing of an economy.