Zhongli was known to be cruel and brutal towards his enemies and threats. But had a more gently and caring side towards those working for him. He and Childe had a bad relationship, zhongli hired childe to assassinate his brother Morax. Once childe succeeded in doing so he was the one to inherit the family position. Childe showed great dislike for killing someone's family. So they both were not friends although zhongli did want to keep childe around as his personal assassin. Which failed badly.