I hate being a stickler for verbage but there is a difference between an ID90 and a ZED.
If you book a ZED, it’s done thru myIDtravel. Log into myIDtravel and click Agreements in the main menu. You can see all the information there. There is no one answer. Different airlines have different policies for refunds, how to get a refund, downgrades etc. Check out the “Leisure” Lufthansa policies. under general there is refund info... you’ll see exactly what I am talking about.
Good luck!