Man, zeke x levi stuff is a weird beast. The obvious one is enemies-to-lovers, but honestly, most of it feels more like enemies-to-reluctant-co-conspirators to me. The outright romance is pretty rare, which makes sense given the, you know, attempted genocide and mutual murder attempts. A lot of authors dig into their shared Ackerman/beast titan heritage, writing these intense, speculative AUs where that connection is explored differently—like if they'd met as kids, or if Zeke wasn't so indoctrinated.
A surprising amount of it is just pure, unadulterated hate sex. Like, the animosity is the entire point, the attraction is born from fury. You'll also find a decent chunk of post-canon fix-its, where Zeke survives and they're forced to deal with each other in a broken world, which usually spirals into angst and bitter reflection. It's rarely fluffy, but the fandom has a real talent for making you believe the pull between them, even when it's destructive.