On the table's homepage, click the link to "Customize this page".
On the customize page, click the link to edit default report settings.
In the default report settings, there is a section where you can select which columns should be defaults. The columns in the right box (Default Columns and also Cassandra) are the ones that Zapier will display. Don't forget to click save when you make changes!
You may also consider selecting the option at the bottom to be prompted about making new fields default columns. Otherwise you will have to remember to come back to this page and edit the list again.