I’ll continue the tartali thread later.. since it’s rather long. I think i’ve also covered most of the in-game things anyway.
Them in one of the official lantern-rite art. Which proves that they have spent lantern rite together at least once.
and in the official Wikipedia page they are described as friends. While it’s not ‘canon’ or written by HoYo devs it’s still looked through and approved so a win?
the both share two voice-lines about the other. And zhongli’s second voice-line about childe ‘drinks’ (that only gets unlocked when you finish the liyue AQ) implies that they still go out for drinks very often even after zhongli’s identity has been revealed.
the gold and blue stones perhaps do represent zhongli and tartaglia. And childe’s material in the bouquet as well.. (when this BD-art was released, childe was the only one who used it)
them with a ginko leaf. In china, it’s a symbol of love. (In Chinese philosophy, the two-part ginkgo leaf unites yin and yang) feel free to correct me.