I used Zavo for a few payments, I was really thrilled with the Zavo Coins and voucher redemption for them but once the 30 day lock in ends, the option to redeem vouchers just disappears, and even on playstore reviews there are a lot of people who seem to experience the same. Other than vouchers you only have trash products being offered at discount which could have been obtained at discount eitherways .
So kind off a marketing gimmick.