How can I change my Z to a R visa.

I have been hired by an American company to negotiate and source products in Shenzhen, They want me to move there permanantly (I currently live and work as a teacher elsewhere) and inspect long going productions. I need to know if it is possible to change my Z (expires on the 30th of December) and get a R without leaving. If not, then can I do this from Hong Kong? What documentation do I need to provide?