This study is for adults with advanced cancers that have a change in the HER2 gene, which is a special part of cells that can help them grow. The study involves a medicine called zongertinib, which is being tested for the first time. Participants will take zongertinib pills once or twice daily. The goal is to find the highest dose that patients can handle and to see if it helps shrink tumors.

The study is in two parts. The first part is for different advanced cancers, and the second is specifically for non-small cell lung cancer with a specific HER2 mutation. Participants will remain in the study as long as they benefit from the treatment and handle it well. Doctors will regularly check participants' health and watch for any side effects.

• Participants can join if they've had unsuccessful treatments before.
• Regular health checks will be needed during the study.
• Participants must be willing to provide tumor samples for testing.