Can I work and study at a university at the same time on a Z visa？？

Yes but are you applying for a job which will get you the Z visa or do you simply wish to get a student visa.

You'll need a job to get a Z (work) visa and you can study if your schedule permits.

You can also apply for a student visa and work part-time if your schedule permits (probably will) but if you decide to stay on and work later you'll need to leave to get the Z visa and return and process a new residency Permit.