Here are miners for Zcash that you can use on graphic cards, EWBF miner, DSTM miner, Bminer, the best graphic cards for Zcash are Rx radeon series and nvidia gtx1070, I don't have info about Zcash performance on new GPUs like the RTX but the truth is zcash is less profitable on gpu this days, if not almost everyone will be mining with GPU right now, you aren't the only one who wants some Zcash through mining