I keep circling back to how they write the weight of history between those two. It's less about romantic fireworks and more about the sheer, exhausting burden of having seen everything, knowing everything, and still having to go through the motions. The best fics I've read frame their emotional tension as a kind of quiet, mutual recognition of that fatigue.
Take this one story where Zhongli is cataloguing relics from the Archon War and finds a feather. The whole fic is just him holding it, remembering, and Cloud Retainer watching from the window, knowing exactly what he's thinking without a word spoken. The tension wasn't in a confession; it was in the shared, unbearable nostalgia for a world they helped destroy and rebuild. It's in the things they choose not to say, because saying them would make the loss too real again.
That silence between them, filled with centuries of unspoken agreements and grief, is where the real story lives. It gets under my skin in a way louder, more dramatic pairings never could.