Levi's not wrong about Zeke, here. He's correctly gleaned through interacting with him that Zeke doesn't care about the lives of people. It demonstrates Levi's keen ability to read others correctly, to see to their true natures, even when working with limited information. It's why Zeke gets so defensive and makes that jab at Levi about not being popular for thinking he knows everyone's feelings. Levi responds with "I do know", because he does. He's got better instincts about who people really are than any other character. The same way he was able to pick up on Eren's monstrosity so early on.
The only thing Levi doesn't have, of course, is context for why Zeke feels that way, why he doesn't show remorse or guilt, why he doesn't believe people's lives have value. But he's not wrong in his assessment that Zeke feels that way.
Which brings me to this next point, which I've spoken about before, about how, in the end, it's Zeke's own doing, his own narcissism which is at fault for why Levi doesn't have that context. He just assumes Levi can't understand where he's coming from, but he makes that assumption without knowing jack shit about Levi himself (exemplified by the fact that he thought Levi would let himself be killed by the soldiers Zeke turned into Titans, rather than go after him), because he thinks of himself, and more to the point, wants to think of himself as uniquely qualified to solve the Eldian's problem. So he doesn't even try to communicate with Levi, to give him that context, simply deciding on his own that they can't trust each other, which goes hand in hand with how Zeke thinks he's entitled to make choices for everyone.
The thing is, Levi did try to understand:
He kept asking Zeke about what happened with Ragako village because he wanted to see if their was any humanity in Zeke at all, any empathy, any compassion, anything he could put his trust in to make him believe Zeke was being honest. If he had shown any of that, any shred of actual pain at having done what he did, Levi would have listened and trusted in him more. But instead he acted glib and completely untroubled by what he had done:
And, despite Zeke's claims to the contrary, Levi actually did show understanding and even agreement with Zeke's position.
Levi agrees that they don't have time to be screwing around, that they need to act as quickly as possible to defend themselves against the coming assault by the rest of the world (an assault Zeke orchestrated with Eren), but then Zeke says this to himself:
Levi literally agreed with Zeke that they didn't have time to be doing what they were doing, but proving that Zeke never had any intention of trying to make himself understood is the fact that he doesn't even seem to have heard Levi agree with him, or that stated agreement was so unimportant that it just went in one ear and out the other. He was dead-set from the start that Levi, and no one else, could possibly understand him and where he was coming from, and so wasn't even willing to consider the possibility of a dialogue.
He's a narcissist with delusions of grandeur, and Levi's assessment that people's lives mean nothing to him is correct. Which is why Levi thinks what he does here:
Levi tried giving Zeke the benefit of the doubt, tried to give him a chance to prove he was a good person, or that he had noble intentions, at least. But Zeke threw Levi's invitation to prove himself back in his face again and again and Levi concludes that Zeke can't be trusted because he's without empathy and a proven liar.
That's just driven home more by what Zeke does next, forcing Levi into having to kill his own comrades and then trying to weaponize his pain over that against him, trying to throw him off by literally mocking Levi's pain, figuratively twisting the knife that he's driven into Levi's heart.
Would anyone in their right mind trust someone who, time and again, displayed this level of genuinely perverse cruelty and lack of empathy?
And yet Levi did try to trust Zeke, despite everything.
It was Zeke who refused to accept that offer of trust.
