I know that you get to control your triggers if they trigger at the same time, and i know this would be HIGHLY INNEFFECTIVE as my tie would be double stressed, but you let me worry about that....

so is it possible with the use of Youngster with expose and a black squad with Decoy to have a tie fighter move at PS 7, shoot at PS 4 and roll 5/6 red dice. 5(r2-3)/6(R1)

No, Opportunist and Zeta Leader's ability can't work together. They both start with giving you a stress, and can't be activated if you're already stressed. And you do have to finish resolving one effect before you can begin the other - they're triggering off of the same event, not off of each other.

If it weren't for the FAQ ruling that Captain Yorr's stress-absorbing ability cancels the resolution of abilities with stress "costs" (specifically naming Opportunist as an example) then that would be an option, but that's a no-go, too.