There are several trains every hour from Zurich Airport to the Main Station of Zurich (Zürich Hauptbahnhof). At the airport station there are ticket counters where you can get advice on buying tickets, as well as several ticket machines where you can easily buy a ticket.
In the main building of University of Zurich there is a canteen where you can eat very comfortably and inexpensively.
In the vicinity of the main building you will find many other possibilities to eat and drink. Below is a small selection, you will find many other ones.