a solution is not the same as a hash.

They are fundamentally different measurement.

ZCash reads out in sol/s because the Devs believe it is a better measure than hashes.

That last sentence makes little sense and is misleading.

OP, it sounds like you were equating the hashrate your cards get ethereum mining to zcash mining. You should just test mining some zcash to see how fast your rig is.

At the moment, your AMD cards are almost certainly 15%+ more profitable mining eth than zcash, but that can change very quickly.