What's the difference between the " Foreigners work permit " and " working permit "

What's the difference between the " Foreigners work permit " and " working permit " Because, my friend is preparing for z visa . She applied it and they have issued her "working permit " on March 5th. She was about to apply for the invitation but got informed it's no longer needed. 1). So can see still use the working permit to go home and apply the Z? Or she need to apply for the" Foreigners work permit ? Aside that, she is non native but she's great and had worked in that school for three yrs..
2). What are the needed documents for Z type starting from April?