Zhong Yao had another concubine, Lady Sun (孫氏), who was very jealous of her husband's other spouses and constantly sought to harm them or make them fall out of her husband's favour. When Zhang Changpu was pregnant with Zhong Hui, Lady Sun attempted to harm her and her unborn child by poisoning her food. However, Zhang Changpu was alert and she vomited out the food when she sensed that there was something wrong with it. Nevertheless, the effects of the poison still caused her to become unconscious for a few days. When she recovered, a servant advised her to tell Zhong Yao about the incident,[3] but she replied:
"Conflict between family members will cause the family to break up. There have been many of such cases in the past. Even if my husband believes me, who else can bear witness to the incident? She (Lady Sun) expects me to tell my husband about the incident, so she will definitely try to preempt me by letting my husband know before I tell him. In doing so, she will end up breaking the news to my husband first. Wouldn't this turn the situation to my advantage?"[4]
She then claimed that she was ill and remained indoors.[5]
As Zhang Changpu predicted, Lady Sun told Zhong Yao: "I wanted her (Zhang Changpu) to have a male child, so I gave her a drug that would increase her chances of becoming pregnant with a male child, yet she accused me of poisoning her!" Zhong Yao said: "It doesn't make sense for you to secretly put into someone's food a drug that would increase a woman's chances of becoming pregnant with a male child" He then summoned the servants, questioned them, and found out the truth. He then asked Zhang Changpu why she did not let him know about Lady Sun's deed, and her reply was the same as her earlier response to the servant. Zhong Yao was greatly surprised and very impressed with Zhang Changpu's virtuous behaviour. Zhang Changpu gave birth to Zhong Hui in 225 and became even more favoured by her husband. Zhong Yao also divorced Lady Sun and made another of his concubines, Lady Jia (賈氏), his formal spouse.[6] Pei Songzhiremarked that Zhong Yao's decision to designate one of his concubines as his formal spouse (even though he was already very old) was in accordance with Confucius's teachings in the Book of Rites.[7] The Wei Shi Chunqiumentioned that there was a rumour that Zhong Yao divorced Lady Sun because he favoured Zhang Changpu. Empress Dowager Bian heard the rumour and wanted to know if it was true, so the Wei emperor, Cao Pi, summoned Zhong Yao to ask him. Zhong Yao turned furious and tried to commit suicide by consuming poison but failed, so he consumed spices until his teeth started chattering. Cao Pi then stopped asking him about it.[8]