Yes, she does hit first and dispel after. Therefore, on her first turn going off, she may get to jynx if there’s buffs in play. However, any hits after that [with jynx] would require the opponent to reapply several buffs in a very short window, before Zeline is charged & goes off again, to really benefit. That, or you’d have to hold off Zeline’s SS so that normal damage might Jynx. & It would require the chance for extra damage to activate before the dispel as well. Definitely not ideal. Whereas, someone like Hel wouldn’t ever have to worry about removing the buffs that make her hit harder; she would just do her thing. So yeah, I wouldn’t use emblems on Zeline for that specific talent; it won’t be as useful on her as it would be on nearly any other wizard. Though, if Zeline is your top/favorite/most versatile wizard, I’d still use emblems on her, but only for the stat boosts, not for the talent itself.
To be fair, Zeline doesn’t need her talent to work 100% of the time to still be amazing, because she’s just that good. However, someone like Hel would be even better for the Jynx job, since she doesn’t remove the buffs that give her a shot at hitting harder. Therefore, more opportunities to do extra damage from Jynx with Hel vs Zeline. Just my thoughts on it though.