I've to point out there's not a coupon option on ZeusHash yet. I do own quite a few referral coupons on zeusminer.com. No way to spend them. Even using these referral coupons, I still cannot afford a volcano.
It seems zeus guys have come up with sth related to coupons, namely hashcode, still under development. In cryptocurrency industry, all thess asic companies are required to deliver sth interesting to customers. Otherwise, we're soon get tired of it.