I think a large portion of that hashrate is all the GPUs switching of ZEC since it's completely an Asic coin now. A few hundred thousand GPUs is less then the hashrate that was on ZEC and there's zero point in GPU mining anything on the Equihash algorithm now.
If all the ZEC mining GPU move to ETH, it will only increase the ETH has rate about 15%. I think that is the ETH ASIC.