You need to understand that traveller is literally a god for himself and he is slowly regaining his power. But you also need to see that in the fight between Childe and traveller, we didn't ACTUALLY defeat him, instead he returned back to his normal form as his Fowl Legacy transform was too much of a burden for him. And about Zhongli, he is obviously stronger than any one Fatui Harbinger (Notice: By one, I mean that he could handle one Fatui Harbinger at a time, we aren't sure if he could handle more at once). Also we don't know anything about Tsaritsa. My guess is that Tsaritsa is actually stronger than all of the Archons INCLUDING ZHONGLI TOO because if she have the power to hand out delusion to others then she could definitely use them and by use I don't mean one, I mean ALL ELEMENTS. Tsaritsa might be able to use all Elements at once. So according to my theory, Traveller>Tsaritsa>Zhongli>Archons>Fatui Harbingers/Adepti Beasts and Yaksha's.