a friend with AMD gpu say me he got nice result with ETH + SIA, it is possible to mine Zcash + SIA with Nvidia ?
Yes it is possible, try Claymore's dual miner: https://bitcointalk.org/index.php?topic=1433925.0
Claymore dual miner is Ethereum only and who wants to mine that, right?!!
If mining Zec then can only mine Zec on it's own.
@BUTUZ There's no dual Zcash miner out as far as I know.
And you can always ShapeShift your ETH for ZEC as you mine it. AMD cards are just better at Ethash, so to maximize daily profit you should be mining ETH and converting.