On models with a slider switch next to the camera (not a keyboard button):
If the hard reset didn't work, the lock is likely software-based. HP ZBooks often come with "HP Client Security" or "HP Sure Click" pre-installed. hp zbook camera button free
Press it, and the camera physically disconnects or a built-in shutter slides over the lens. A small LED light usually toggles to let you know the status. On models with a slider switch next to