I am not sure if it is even possible for Zeta Leader to use Opportunist. He practically has it built in, both are take a stress to roll an extra die, but both of them require you to not have any stress to start with. I've had some people say that the 'take a stress' events happen simultaneously and allow him to double stress to get two attack dice, but I am not sure about this. If they do have to happen in a sequence then it becomes impossible for him to do one and then the other. Any ideas?

It is impossible. They do trigger at the same time, but as there is no way to "nest" them you have to resolve one fully before moving to the other, which will then find a stress token preventing it from working.

He's built for Wired and Weapons Guidance.

Just like Omega Leader is built for Juke and Comms Relay.

Nothing happens simultaneously technically. Anything that 'happens at the same time' must be resolved in your chosen order, so the event is actually now back to back.

Simultaneous firing...

Simultaneous firing...

Which isn't actually simultaneous. You completely resolve one attack before moving on to the next. If Whisper has initiative and deals the final card to Wedge and it's a Weapons Failure crit, Whisper will recieve a focus token for hitting, cloak via ACD and then Wedge will roll one less die when attacking. If it was simultaneous instead of sequential, you would delay Whisper's focus and cloak and Wedge would attack at full strength.