Swiss Travel Pass or Swiss Half Fare Card

For just 2 days, I would not bother with either.

The half fare card is CHF 120. So, you'd need to spend CHF 240 just to break even. A 3-day Swiss Travel Pas is CHF 244.

I have another question about traveling. I need to get from the Zurich Airport to Mulhouse, France. Can you suggest a website where I can purchase a train ticket. I do not mind 1 transfer if necessary. I have not had luck so far as the only trains I found were early morning departures. I need one that leaves at noon or after.

https://www.sbb.ch/en

Use the SBB website:

https://www.sbb.ch/en

You want Zuirch Flughagen (airport) to Mullhouse. You can change the date and time of departure. It looks like there are at least 2 trains every hour.

Every 2 hours, at 34 past odd number hours there is a French TGV from Zürich HB to Paris Gare de Lyon which stops at Mulhouse with the only change being from the train from Zurich airport to Zürich HB. It is an international TGV and will carry a high price.

Alternatively,

For normal trains, to Mulhouse from Zurich airport you may have to change at Zürich HB but you almost certainly will have to change at Basel SBB. The local French trains between Basel SBB and Mulhouse use the old French station attached to the main Swiss station, and using tracks 31-35. You walk through what used to be, before Schengen, French and Swiss immigration and customs booths, now decommissioned and into the the old French sector. Allow about 5 or 10 additional minutes for the change.

Sounds complicated - it isn't.

Thank yo for this information.
Do you think I am too early in trying to make a reservation for June?

yes