One may not legally teach in China without both the Z visa and a valid Resident Permit.

Most Chinese employers will insist that you teach before your Resident Permit is issued to you. And most, if not all, foreign teachers who have moved to new positions will find themselves caught between a rock and a hard place. I've been in that position every time I moved to a new teaching position. As a new foreign teacher at a new school, I felt obliged to keep my new employer happy as my first priority. So, I said nothing and taught illegally, as I'm sure most of the other FT's in China who change jobs, or take up their first teaching appointments, have and will continue to do. A degree of common sense is required here - go with the flow. Remember, this is China. Don't make unnecessary trouble for yourself! ,