Are Vietnamese surnames such as Chen and Zhang immigrants from China?

Historically, north-central Viet Nam has long been the territory of China. In 968, it officially became independent from China. After that, Vietnam experienced several feudal dynasties and continued to expand southward, but all the dynasties were vassals of China.

So,

Vietnamese surnames such as Chen and Zhang are most likely from China. Of course, due to the integration of some races, new members also have these surnames.