Create an action from your zip-code sheet to your first sheet. But don't pass any variables. Click "Selected field" but don't add any fields in the list.
Here's an edit box for one of the actions where I do something like that:
Mine is using a little sheet called "Return to Main" that looks like an icon. But you can do it directly from your zip code sheet the same way.
Notice that I have all my sheets selected on the target dashboard. That's not really necessary. Any sheet on that dashboard will do.