Awww that's hard! I was in love with Shen Wei from the get-go, esp after seeing him as the Envoy, but I liked ZYL a lot, too. My favorite thing about him: his sheer competence. He likes to disguise it with a lot of literal handwaving and "oh wow, bro, tell me more" naivete, to make ppl underestimate him, but he is SO SMART and strategic, and uses his shamelessness like a weapon (the sleeping on SW in the car! the SECOND sleeping on Shen Wei in the car he wasn't even supposed to be in!).

Also: by the time you get to the mind-control episode, I deeply love all his attempts to make ROOM for Shen Wei to tell him the truth, which he has already figured out for himself. That little scene just after the wedding where he gets intensely unhappily quietly frustrated that Shen Wei still won't tell him, but still doesn't push him to the brink, mannnnn I feel for him so much. And then the super badass "use the gun" moment, MY HEART. They are so in tune there.