These days I saw pool hash rate increases almost twice e.g. flypool, while total block found remains constant. Can I make the conclusion that there is constant mining rate for each pool?
I think this post will answer your question.
I understand now. The total hash rate increases everyday with the Zcash price remains high for several days. Lots of miners transferred their rigs from ETH/ETC to Zcash. it makes the profits of zcash miners decreased to a level that no new miner jump in until it is stabilized.