MRB has released the latest version of SilentArmy ZCash miner (v5), and so far it is the fastest open source miner out there – even faster than Claymore’s ZEC miner (taking into account the fee). There is another upside – it uses much less cpu power too.
This is mostly a linux build, but it is available for windows. You will have to compile it yourself, but some users have posted compiled binaries available for anyone to download. Be careful again what you download onto your machine. You can expect 75-80 sol/s for a Rx470/480, 90-100 sol/s for a R9 390, 40-50 sol/s for a R9 380, 75 sol/s for a 280x. For Nvidia, some users are reporting almost 100 sol/s on a 1070 but results may vary and there is still room for optimization.