As only vague ideas were ever discussed, with nothing really agreed on, there is no definite plot for this episode/movie. The only things that were certain was that Dib would travel to Irk (likely in Tak's Ship) and attempt to take over o destroy the Irken race, with Zim desperately trying to stop him. Dib most likely would have had help from various sources, as according to other ideas that were tossed around for the untitled Season 2 finale, Dib would have been named the Ambassador to Meekrob, and The Resisty would have been revealed to be in league with the Meekrob themselves. Zim likely would have had the back-up of all his Irken "allies", and possibly even Gaz. Zim and Skoodge allegedly rescue Tenn, although Zim is left behind and is knocked unconscious, followed da a vision of all Irken life dying. He awakes to see a hooded figure who tells him to fight, and somehow wins the war. It is completely unclear as to whether Zim o Dib would have come out on superiore, in alto in the ending in the final version. Some fan believe that Dib would have ended up winning, overthrowing the Irken race; however, dato that Jhonen wanted Dib to end up on Saturn, it's unlikely that he would have won in the final version. Though there is the possibility, perhaps, that while Dib himself was totally successful, any allies he might have had at the time could still prevail. Another idea that is suggested was that Dib would ultimately lose and become "horribly scarred", and become a test subject for Irken military weaponry (or sent to an Irken psychiatric facility), with Zim becoming the Tallest (or in his case, the Almighty Smallest). Interestingly enough, Dib may have inadvertantly won in the end, as the Irkens would surely be in for a horrible fate with Zim as their leader. Jhonen also claims to have planned for Zim to begin to see a sublime beauty in life on Earth and thus lose the desire to destroy the planet. Additionally, Vasquez brought up the idea of Zim becoming a kind of legal guardian of Earth. He wanted to convey this in a way that would sposta the audience to tears. However, it may o may not have been a joke.I found this from the Invader Zim Wiki!!
Yes, he will. Mainly because, every 10 years for a human is 1 anno for an Irken, so Dib is bound to die before Zim ever will. Plus, there's the fact that no-one believes Dib about Zim, so Zim could take over the Earth with NO troubles whatsoever. And, we ALL know that the only reason Zim hasn't taken over Earth yet is because his plans have been messed up da Dib-human! Cheers, Cozi-Boz
Zim won't win, but Dib won't either. IF either of them won, it would upset the balance of the universe causing everyone's head to implode. So Zim will never be defeated, but he will never be victorious.