I´ve got a work visa Z, resident permit, I will quit my job soon.

Fabio, you can change the Z tpe into a one-month L type at the Exit and Entry Administration Department in mainland. However, I'm not sure whether the one-month L type can be extended. If you want to stay for two months or more, before the L type expires, you should go to the department again and see whether it can be extended. If not, you have to leave China and apply for the L type again.