It has been confirmed that “t1ZYZS6ynUDbvht7vH3dMiM3rsAJ1p6EGWC” is a public Antpool for Zcash which has 1M Sol/s ~ 2M Sol/s of hashrate and has been around since Nov/04/2016 .
https://explorer.zcha.in/accounts/t1ZYZS6ynUDbvht7vH3dMiM3rsAJ1p6EGWC
“t1S4ydQEgzgLuWWvHiRBfcqW7AFE3RssVHy” (BITMAIN’s ASIC Private Pool suspect) is still unidentified.