is there a any chance z cash can cheaper than today price within 2 month due to volume increase
Since its beginning ZEC is only going down as far as I know. There are no signs it will go up in the future, but the the price is falling not because the volume is increasing. It is falling because it was set too high for this coin in the beginning of November 2016 when it was first put out to tender.
May you need read again about the economic basic theory, it seems like economy 101 is very suitable to be applied on the zcash case.