UPS did not have their account number on their invoices.
Therefore, after checking with them, I confirm that the German UPS IBAN is:
DE30 5121 0600 3223 3350 21
DE30512106003223335021
The account owner is
United Parcel Service Deutschland S.A.R.L. & CO.OHG
If you get a payment request from UPS to pay to this account it is legitimate.
Please note: UPS does “Lastschrifteinzug” using a different bank account.