It is not a problem of Mining Pool, but it is a problem of Zcoin that provides the hash-rate of the network and the difficulty, I believe that the calculation of the difficulty (last 6 blocks mined) is completely wrong ...
Zcoin developers should explain this:
141.8094 GH/s difficulty 19715 (now)
145 GH/s difficulty 25300 (a few day go before the fall of mining pool hub)
There is no mathematical sense to these data, I hope that the problem will be solved as soon as possible ...