I will be flying Chicago to Dublin to Zurich all on Aer Lingus so no changing terminals. When will I go through passport control? Thank you
In Zurich. Ireland is not part of of the Schengen Treaty.
Dublin airport has a flight connections guide you can download:
https://www.dublinairport.com/flight-information/connections/connection-guide
Remember, if flying back to the US through Dublin, you will go through US immigration and customs in Dublin. When you arrive in the US, you will walk off the plane as if it is a domestic flight. Make sure you have time to do that.