I switched my Z9 minis (6) about 2 weeks ago, and happy with BTC :-)
are you saying that your z9's mine zcash and prohashing pays you in btc?
At prohashing you can mine zcash only or even better multiswitch between coins for equihash algorithm and you choose which other coins you wan't it converted to like BTC and or LTC and or ...
You set this in "settings".
The conversion is done at once.
You follow this "live" under "earnings".