You will enter the Schengen area in Zürich, because Geneva is a domestic destination (both in the sense it is within the same country and within Schengen). Therefore, you will pass through border control in Zürich.

Whether you need to go through customs in Zurich on a connecting flight depends on your specific travel route and whether you are entering the Schengen Area.

Here’s a quick guide:

1. If you are arriving from outside the Schengen Area and connecting to a destination outside the Schengen Area:

• You will not go through customs or passport control in Zurich.
• You will stay in the international transit area, simply changing gates.
• Example: New York → Zurich → Singapore (no customs in Zurich).

2. If you are arriving from outside the Schengen Area and connecting to a destination within the Schengen Area:

• You will go through passport control (immigration) in Zurich, because you are entering the Schengen Zone.
• After passport control, you collect your checked luggage (if any) and then go through customs before checking your bag again for the Schengen flight (if applicable) or heading to your gate.
• Example: Chicago → Zurich → Paris (you clear immigration and customs in Zurich).

3. If you are arriving from within the Schengen Area and connecting outside the Schengen Area:

• You will go through passport control (exit check) in Zurich before your departing flight.
• Usually no customs check for leaving Schengen, but there may be occasional spot checks.
• Example: Rome → Zurich → Tokyo (passport control in Zurich before the Tokyo flight).

4. If both flights are within the Schengen Area:

• It’s like a domestic connection — no passport control or customs.
• Example: Barcelona → Zurich → Vienna (no border checks in Zurich