In 477, after Xiao Daocheng had seized power after assassinating the violent Emperor Houfei of Liu Song and made Emperor Houfei's brother Liu Zhun emperor (as Emperor Shun), the general Shen Youzhi rose against him from Jing Province (荊州, modern central and western Hubei), and as Xiao Ze defended Penkou (湓口, in modern Jiujiang, Jiangxi) in preparation for a possible eventual attack by Shen, he made Xiao Zhangmao his assistant in reviewing the troops. After Shen was defeated, Xiao Zhangmao initially returned to the capital Jiankang to serve under his grandfather, but subsequently was made the governor of Yong Province (雍州, modern southwestern Henan and northwestern Hubei).
In 477, after Xiao Daocheng seized power and replaced Emperor Houfei with his brother Liu Zhun, the general Shen Youzhi rebelled from Jing Province.  Xiao Ze defended Penkou against Shen's potential attack while appointing Xiao Zhangmao as his assistant in reviewing troops. After Shen was defeated, Xiao Zhangmao initially returned to Jiankang but later became governor of Yong Province.