You need the actual long and lat to do the distance calculations - you can't use those "generated" by tableau in formulas
You can get the zip centroid long and lat from US Census bureau Tiger files - the file is extensive so if you are confined to a state you can filter to that state before downloading
but bear in mind they are not street address longs and lats - they are the long and lat of the center of the zip code area
you can then use the longs and lats in the Distance spatial formula in Tableau
If this posts assists in resolving the question, please mark it helpful or as the 'correct answer' if it resolves the question. This will help other users find the same answer/resolution. Thank you.
Jim, thank you for your reply. I did exactly that yesterday, (could not wait, but your confirmation to know you cannot use the lat and long in Tableau is good info) I ran the csv file through prep to separate and name. I then brought in the exact long and lat of the clinic, modified the spatial formula, and wala! LOVE me some Tableau. In the tabular report I had created a filter for > 30 miles< to be Ok to See, and Do not see. By accident I applied that filter to my map and it was brilliance!