I mean, the thing about Zim is that despite what he might say, he is absolutely capable of love and affection. It’s just that he only expresses it to a very select assortment of people.
First and most obvious one is probably his relationship with the Tallests. Which tends to be a lot less just a ‘loyal soldier duty bound to serve his leaders” and is coded a lot more like…. “Child overeager to please his neglectful parents”. I mean, the entire emotional crux of ‘Enter the Florpus’ is built on this.
Zim isn’t just motivated by a pure ideological belief in the Irken Empire’s conquest, or by the desire for the fame and accolades that come with being a successful Invader. I mean, those ARE factors. Zim is both a true believer in Irk’s imperialist ideology and very interested in feeding his ego. But he’s also looking for a more personal sort of emotional validation specifically from the Tallests. One that he’s desperate for, but we know that he’s never gonna get.
(And that’s not just because Zim sucks. Even if he could somehow stop being a walking disaster area and a giant millstone around the Empire’s neck, that desire for the Tallests’ love would still be a fool’s errand. We’ve all seen how they treat poor Skoodge.)
In addition to that doomed attempt at an emotional connection, Zim can sometimes be kinda affectionate with his various robotic minions, which obviously goes back to the whole…
And that same episode ends with him having a very similar sort of response to Robo-Dad and Robo-Mom picking him up.
And then there’s, of course, his M-Lab Robot Minions in 'Enter the Florpus'. All named - and all grieved by him.
His extreme reaction to Lawrence specifically dying shows he did apparently see them as individuals.
But as far as we can tell both the Roboparents and the Robot Army are not, like, sapient? I mean, AIs like GIR or the Computer are characterized as basically Machine People - but these robots barely seem more sapient than my laptop. And as much as I love my laptop it’s not gonna, like, love me back.
Speaking of GIR, he’s another example of someone Zim shows genuine care for. I mean… he can absolutely be pretty mean to him at times…
But any sort of kindness from Zim has to be graded on a Curve because he’s so terrible. ‘Hobo 13’ demonstrated to us very well just how horrible Zim can be to his subordinates - rude, inconsiderate, pretty much deliberately sacrificing them not just for his personal gain but also just for his own petty amusement.
And it’s notable that’s not how he treats GIR. Who he expresses actual concern for…
And he pretty easily acquiesces to GIR’s capricious desires even when he clearly sees them as Stupid and frivolous.
This scene is especially notable. I mean, this is Zim actually feeling bad about the fact that he made someone cry and trying to de-escalate the situation. Maybe for other characters a moment like that would be no big deal, but this basically the softest Zim has been through… all official IZ media. And it was a scene with GIR.
And meanwhile GIR himself… didn’t really register any of this - either Zim’s frustration or his attempts at sort-of comforting him, because he was only sad about having eaten his cupcake and not being able to eat it more.
Because that’s the thing, while GIR does have some level of affection towards Zim at times…
He doesn’t really show that same level of care. I mean, in pretty much all of these examples, GIR puts his own desire to give Zim physical affection over Zim’s clear discomfort and disgust. And in general, while GIR vaguely acknowledges that Zim is his master - he often disregards or ignores Zim’s orders and requests. And not just when it comes to being ordered around in yet another evil scheme -
But also when the situation is just clearly basically hazardous to Zim’s very life.
(Which is very much in contrast to Zim, who, again, is actually emotionally invested in GIR’s safety)
While some of GIR’s inability to fulfill Zim’s commands can be attributed to his lack of mental focus and general stupidity - his absolute lack of care and regret about these situations seem to imply that, like, GIR might follow some of Zim’s orders when they seem fun, and he might like Zim in the sense that GIR is generally incapable of genuine malice. But GIR is never going to care about Zim, as a ‘Master’ or as a friend, as much as he cares about his own hedonism.
And of course, we all know that if GIR was capable of actually focusing on anything and remaining grounded in reality - he would very quickly realize that he actually hates Zim quite a bit.
And that’s, like, the whole Tragedy of Zim. He is a being capable of kindness and friendship - but he always ends up only caring about beings who will never care about him back.
Due to Irken indoctrination and also self-inflicted due to his own ego (like, it is no coincidence that the People Zim Actually Cares About are the two beings Irken ideology obliges him to acknowledge as his superiors and then a bunch of robotic minions who are supposed to be 100% obedient to him.) Zim only loves those who will not love him back.
Except for Minimoose. That relationship is 100% wholesome.