In it, he was a prodigy genius as a child (of course). Mother died while young and Varis rarely had time for him and he basically saw his servants as automatons.
Then when he was 14, he got a new combat instructore. A master swordsman from southern othard. He kicks Zenos' butt every day and at first he can't even follow his movements. Then little by little Zenos starts to learn and improve, until he's able to fend for himself more. He starts studying the swordsman's style and eventually learns it by examining him, even if it means allowing himself to get hit sometimes in training to get a better look.
He's eventually able to replicate the style, even the aether use, by embedding a crystal into one of his palms. Said to be dangerous but Zenos is able to use that to force his body to release aether. The conscripted trainer flips out that Zenos is learning his special sword style and attempts to kill him but Zenos defeats him and kills him. It also plants the idea i Zenos' head that the inability of garleans to use aether naturally is a weakness that needs to be dealt with.