Exiting and reentering China using a Z type

I am currently on a Chinese Z type- working as an English teacher in China. My Z type type will expire in September 2017.

I have holidays from my school in July and August. Would it be possible for me to leave China in July to travel to South Asia, and then reenter China in August to travel for about 20 days in China, and then leave back to my home county using my Z type, or should I apply for a tourist visa?