OP already hired H-1B in the past and that person is working for them now. OP is now in the process of doing a green card application for said employee. They can't move forward with the GC application because there are other qualified citizens/residents, but they don't have to fire the existing H1B employee.
That's how I understand OP, if that's legally true or not, I don't know.
That's how I understand OP, if that's legally true or not, I don't know.