During the reign of his brother Zhang Chonghua, Zhang Zuo was trusted by his brother, and despite warnings by Chang Ju () and Xie Ai, Zhang Chonghua, for a long time, intended for Zhang Zuo to serve as regent for his son Zhang Yaoling. Late in 353, however, as Zhang Chonghua was gravely ill, he ordered that Xie be recalled to be warrant—but Zhang Zuo and Zhang Chonghua's attendants Zhao Zhang () and Wei Qi (), who had conspired to take over power, blocked Zhang Chonghua's order and instead forged an order making Zhang Zuo regent. Zhang Chonghua soon died, and he was succeeded by Zhang Yaoling, at age nine, but real power was in Zhang Zuo's hands.