Is it permissible for a radiologist and ultrasound technician who feels the need for further learning and is not yet specialized, to teach a gynecologist how to use the ultrasound machine, knowing that this gynecologist intends to place the device in her clinic and charge patients fees, and she is also not specialized in ultrasound?

The medical field is serious due to the potential harm it can cause to lives and bodies, and the Sharia (definition) has clarified this. The Prophet, peace and blessings be upon him, said: "Whoever practices medicine without having been known for it before is liable," and in another narration: "Whoever practices medicine and is not known for it is liable." Since you are a practitioner and not a specialist, and you need to learn and do not know much in this field, it is not permissible for you to teach the aforementioned woman or anyone else anything they seek to learn from you.