How to pronounce the word "_" in "Zu _"?

Zu _, whose real name is Jing Shuo, is the son of Zu Chongzhi, a mathematician and scientist in the Southern Dynasties. He has served as a magistrate, and his date of birth and death is unknown. Influenced by his family, especially his father, he loved science since childhood and was particularly interested in mathematics. In 462, Zu Chongzhi compiled Da Li Ming according to three suggestions of his ancestors.

According to scholars' textual research, some entries in Zhuanshu were written by Zu _. Zu _ devoted himself to reading all his life, because he thought about problems while walking and made many jokes. Zu _ principle is a method to calculate the volume of a sphere, and it is the most representative discovery of Zu _ life.