Taking the train from Zurich HB to Florence (transfer in Milan). How early do should I be at the station?

Basically the title, but I’m taking an 8:30a train on a Sunday and don’t know how early to get to the station.

I’m pretty inexperienced with train travel in Europe, taken the Eurostar Paris to London, and got to the station like 1.5 hours before. Not sure if this is different since I’m staying in the EU?

Thank you!