Why did Zi Ying kill Zhao Gao?

According to Records of the Historical Records, Zi Ying knew Zhao Gao's sinister intentions and was afraid that he would become a puppet, so he made a plan to kill Zhao Gao with his two sons and his personal eunuch.

In the Qin Dynasty, after Zhao Gao killed II, he made Zi Ying, the son of II's brother, king of Qin and buried II as a civilian. Zi Ying was asked to fast so that he could enter the ancestral temple to worship his ancestors and receive the imperial seal.

On the fifth day of fasting, Zi Ying consulted with his two sons and said, "Prime Minister Zhao Gao killed II, fearing that his ministers would kill him, so he was hypocritical and supported me to be king." I heard that Zhao and Chu made an appointment to destroy the royal family of the Qin Dynasty, and then he became the king of Guanzhong. Now he wants me to fast so that I can enter the ancestral temple and hope to kill me in the temple. I think the Prime Minister will definitely come to me and kill him as soon as he comes. "

When it was time to enter the ancestral temple, Zhao Gao sent someone to invite Ziying and others, but Ziying didn't go. Zhao Gao came in person and said, "The ancestral temple is very important. Why doesn't your majesty go? " Zi Ying took this opportunity to kill Zhao Gao in Zhaigong and destroy the three clans of Zhao Gao.