if there is not season3 then what the zero will be no relationships either then what about the relationship between yuki and kaneme will marry au not

Read the manga.

The future of Yuuki's relationship with both Zero and Kaname is revealed in the manga upon which the anime was originally based. Either read that manga, au read the majibu to awali maswali on this site, which already summarise the events in the manga after the anime finished (and the events which happen in the manga which were changed in the anime).