Why ZCash Nethash increase so quickly?

ZEC:Current 586.86 Mh/s, increase 37.2%
ETH: Current 131.87 Th/s, increase 2.6%

Even with GTX1070, ETH should be more profitable than ZEC, RX580 rigs have better ROI than GTX1070。

It’s called nicehash.

1/5 of hashrate comes from there…

I remember when nicehash went offline the nbethash from almost every coin when 20-40% down