>>492689543>I don't remember reading anything about him putting in the effort to reach that level either.There was one lodestone story that showed it, actually, but you have to go out of your way to read it so I don't blame you for not knowing.
tl;dr: Varis is a terrible father, and he decided the best way to raise Zenos to be a good prince was to forbid him from having friends or going out and making sure all of the mentors in the palace in charge of his education would be completely detached from him and not bond emotionally or anything, which resulted in the permanently bored and also detached Zenos you know. Then he went one step further with his combat instructor, taking a samurai from Doma that Garlemald captured and enslaved to teach him, and who decided that while training Zenos he'd actually try to murder him and pass it off as a training accident. Varis' idea was that the samurai can use aether and Zenos' can't, so if Zenos manages to beat him then surely he's gonna be super imba, right? But that's exactly what the samurai was banking on, that he'd just unleash a really strong attack at some point and "accidentally" kill him. Zenos realized, and what he did was that he cut fucking holes into his arms with his katana one of the nights before training and jammed aether crystals in it, which let him briefly channel aether as well, and he killed the samurai instead. This was the first time in his life he actually felt satisfaction and a sense of accomplishment, so he became the combat autist you know, and from there he started murdering every one of the best combat instructors his father could gather until he became that op.
Plus, he does have direct unsundered Ancient genes, though it's unclear how much do those count. And in SB he gives himself the fake Echo.