Gonna make a list of Zhongli Oddities-
We have no idea where Zhongli comes from, what kind of "being" he is, beyond being a god.
We know all other Archon's original form except Zhongli. Venti -> Wind Spirit, Ei and Makoto -> Electro Demons/Yokai, Rukkhadevata and Nahida -> Literally parts of Irminsul, Egeria -> Creation of the Shade of Life to replace the Hydro Sovereign as the heart of the primordial sea, Focalors -> Loyal Oceanid Follower of Egeria, Pyro Archons -> All Human. Zhongli -> ????
There's mentions of Zhongli having taken on many forms over the years in the Rex Icognito books as well as as a rumour from a Sneznahyan dude, but Zhongli says there wasn't nearly as much shape shifting involved as rumours say.
Zhongli randomly showed up, "descended", right before the Archon War and absolutely decimated the Gods in the surrounding areas.
Zhongli was the first to mention that Traveler is the only "true" record Teyvat has and mentioned that no other physical records are reliable.
Liyue Visions are the only square ones.
Zhongli's Statue of Seven holds a cube and not a sphere like everyone else.
Zhongli's Statue will be surrounded by cubes when you resonate with Geo, the other ones kind of just shine in a circular pattern with the colour affilliated with the element.
Zhongli is never shown with a face in those 2D animation cutscenes, every other Archon is.
Zhongli is the only Archon without a double.
Venti -> Bard in old Mondstadt, Ei -> Makoto, Nahida -> Rukkhadevata (granted only part time), Furina -> Focalors, Mavuika -> She's kind of her own double??? Sorta??
Zhongli's Character Story 5 is slightly altered after the Irminsul Shenanigans. I am however not sure if that's meant to imply that he KNOWS or not. It is specificially not something that was retroactively changed in general (like just a minor general update to the wording) it specifically changes after completing the Archon Quest.
Not necesserily an oddity but something that still sticks out; Zhongli is currently the oldest living being we know/have seen, he's confirmed to be the oldest Archon, being at least 6000 years old.
Zhongli is constantly depicted with Solar imagery, that is otherwise only seen in Decarabian, Deshret and Remus, all being God Kings.
The symbol on Zhongli's back being also found in Deshret's Mausoleum.
Zhongli being able to just like that create gold -> Deshret seems to have been able to do the same; the gold you find in the desert's underground area's is not Mora.
Zhongli seems to be avoiding going by his demon name Morax; Xiao gets weirdly defensive if you do refer to him by Morax instead of Rex Lapis. Other old beings also don't call him Morax but instead Deus Auri (Neuvillette - who technically not that old, has memories of the previous Hydro Sovereign and Orobashi)
You can name Wanderer every Archon's demon name, except Morax.
Zhongli and Neuvillette having funny conversations if you switch them in and out of your teams. (seriously it's funny and I have a hard time believing this is a coincidence)
Zhongli's Character Quest not being the same title as his Constellation while every other Archon follows that Schema. Only exception is Neuvillette, but we know Neuvillette doesn't have a constellation and the one we see in his profile is a fake one he came up with to entertain the Melusines.
Zhongli is the only character (that isn't Dainsleif) that seems to have concrete info on the Abyss Sibling but made a contract with *someone* that doesn't allow him to speak about it.
Zhongli has never said the Line in the Geo Gemstone, every other Archon has.
This one is a little bit of a strech.. maybe? Since it also applies to Furina... but I suppose technically she isn't an Archon anymore?
Anyways, no Honkai Expy. Venti -> Wendy, Raiden Ei -> Raiden Mei, Nahida -> Theresa, Furina -> ??? (People seem to say either none or Sin Mal), Mavuika -> Himeko, Tsaritsa -> Will most likely be Bronya based on Childe's Beta Voicelines.
One of Zhongli's titles in Chinese translates to "Sovereign Lord Rock King" with the character for "Sovereign" being the same that is otherwise exclusively used for the Dragon Sovereigns.