Thinking about a species swap that really digs into how Dib and Zim are products of their environments and what changing those environments does to their characters. How is Irken Dib made different by being raised in an amoral society that indoctrinates people from birth and how does Zim being raised in a society with a concept of morals and ethics change him?
Irken Dib doesn't have Zim's delusional overconfidence and self-centeredness. But like any typical Irken, his own wants and needs come before anything else. He is capable of cooperating with others for mutual benefit, but wouldn't think twice about abandoning or betraying someone to serve his own ends. He has no respect for the sanctity of any life outside his own and the Tallest, and would kill without hesitation or remorse. He isn't motivated by a desire to be seen as a hero, because there's no such thing as heroism in Irken culture. The Irken concept of what makes someone a "good" person who deserves to feel good about themselves has nothing to do with living up to a standard of principles. A model Irken citizen is just one who provides value to the Irken Empire.
Irken Dib has the same drive to win the Tallests' approval as Zim. But what makes Dib still recognizably Dib is that he refuses to pursue that goal through traditional means. Dib was bred to be an Invader, but insists on pursuing a field of study that isn't considered legitimate or respectable in Irken society, just like canon Dib. So his goal isn't to succeed at something that already comes with a lot of prestige that everyone says he's not fit for like Zim. His goal is to convince everyone that the thing he wants to do deserves the same amount of prestige and respect as being an Invader.
Human Zim on the other hand comes from a society that worships and glorifies "heroes" who embody a specific set of moral values. So where Canon Zim couldn't care less about being a good person and has basically no lines he wouldn't cross, Human Zim would want to see himself as a good person and fantasize about being a "hero". He's still a shitty person, he just relies on a lot of mental gymnastics to justify his behavior fitting into a moral framework. He's a bully, but everyone he picks on "deserves" it for one reason or another. But he's still just a kid and has some aversion to crossing certain lines. He couldn't kill someone and be unaffected the way an Irken could.
However, like Canon Dib, it's easier for Human Zim to morally justify taking out his pent-up frustrations on Irken Dib through unprovoked attacks and unnecessary cruelty because Irken Dib is "evil" and inhuman, so the rules of basic human decency don't apply to him.
Human Zim doesn't have an interest in the paranormal that makes people call him crazy, but he's still an outcast because he's a jerk. He's got major 8th Grader Syndrome (aka Chunibyo) and constantly postures about being superior to everyone else while lying his ass off about everything he wants to be seen as cool for.
He's more or less an ordinary kid, so he doesn't want to take over the world like Stewie Griffin. He just thinks he's smarter than everyone else and if he did rule the world everything would be better. His goal is to expose Dib as an alien. But only for the glory. Not validation of his beliefs, fascination with the unknown, or genuine concern for the well-being of humanity. It's purely about the fantasy of being The Special destined to save the world and be worshiped forever as a hero.
Give it a few years and human Zim will become one of four things:
Toxic social media influencer.
