This is an excellent one!! I love jealousy for this ship <3 Here's a little something:
“Does she have to do that?” Childe asks, then cringes, realizing too late the harsh tone he’s taken.

Zhongli glances at him, confused. “Miss Xinyan was merely expressing her gratitude for my support.”

Childe huffs and turns away. He feels hot and prickly and all out of sorts. It’s unnerving how easily Zhongli (and the many, many people who constantly flirt with him) can get under Childe’s skin.

It shouldn’t matter. Zhongli fucks him, but that’s all it is. Childe doesn’t want anything more. (He does. He desperately does.) And Zhongli has made it clear he’s not expecting commitment.

“Is this a Snezhnayan thing, perhaps?” Zhongli asks. “To disapprove so strongly of a little flirtation?”

Childe rolls his eyes. Zhongli probably understands Snezhnayan customs better than Childe himself, given his age and his love for culture and history.

“No?” Zhongli looks amused. It’s both endearing and annoying. “Then what?”

“It’s nothing.”

Childe turns away, taking a step towards the door, but Zhongli catches his arm and pulls him back. Fixes him with that steady golden gaze, pins him in place to watch him squirm.

“You’re not jealous, are you?” All pretense aside, Zhongli’s eyes are narrow and intense, his mouth a firm line. “You cannot possibly be jealous when you have sworn yourself, body and soul, to another.”

Childe opens his mouth, then closes it. Zhongli’s voice has taken on a divine resonance, thrumming through Childe’s bones, and his eyes are glowing.

“Do you know how it eats at me? To know you would offer yourself first to the Cryo Archon, and reserve only the scraps she does not find useful to give to me. You worship another, and yet you complain to me because some sweet young woman touched me on the arm when she thanked me for my help.”

His heart thudding in his throat, Childe takes a step forward, then drops to one knee, looking up at Zhongli.

“I would give myself to Rex Lapis,” he whispers reverently. “If he would have me. If he would risk the Cryo Archon’s wrath, and take a child of the Abyss into his fold.”

Zhongli’s fingertips brush Childe’s forehead, and it feels like a blessing, a kiss of the divine.

“I promise to cherish and love you, to provide for you, to protect you,” Zhongli says. “This is my contract, and it is as solid as stone.”