This study is being done to see if a drug called disitamab vedotin, alone or with pembrolizumab, works to treat HER2 expressing urothelial cancer. It will also test how safe the drug is for participants. Participants will have cancer that has spread in the body near where it started (locally advanced) and cannot be removed (unresectable) or has spread through the body (metastatic). It will also study what side effects happen when participants get the drug. A side effect is anything a drug does to your body besides treating the disease.