Do i need to change my Z visa if i leave my job/leave the country and want to come back?

Hi, i hope you can help me.
I have a Z visa through a job i am with now that i will leave in a few weeks, after i leave i will go overseas for 2 weeks and then i will come back to China. I have used 3 tourist visas already, and i have an invitation for an F visa. Do i need anything from my (soon to be) former employer, or can i just leave, they cancel my Z visa and I apply for a business one before i go?

Thanks.