Zeta stormtrooper

Nope. Unless it's Daka. They'll refund THAT Zeta.

I have a Guildmate with a Zeta Cassian...

Get over it, they gave you a chance by asking if you are sure. Plus....the ST zeta isn't that bad, it's useful. Zetas aren't that rare I get 20 about every month, that's not terrible. Just be more careful in the future, plan your zeta equips one and two toons down the road! That ensures you stay on task buy setting a goal. So far I haven't regretted one zeta.