maybe zcash will remove from poloniex ? who now ?

From where did you get this "information"?

i ask only ? why in poloniex a long time the ZEC wallet is in in maintenance ?

Don't know, but I guess if they would want to delist it, they would write that, as they did several times before with other currencies.

It is activated now. However, there is some missing coins there so I have contact them again.