Zip Code Populate city and state?

Where are you going to get the zip code information?

https://gis.stackexchange.com/questions/53918/determining-which-us-zipcodes-map-to-more-than-one-state-or-more-than-one-city

If you had a table with Zip Codes, you could use something like this in "Trigger after update".

let myCustomer := this;
City := text((select ZipCodes)[ZipCode = myCustomer.ZCode].City);
State := text((select ZipCodes)[ZipCode = myCustomer.ZCode].State)

You could also use an API to get the city and state info.

https://www.zipcodeapi.com/API

Nice!

Can't use http() in a trigger, so it would have to be a button or something. You would need an API key. 

Use this API to find out the city, state, latitude, longitude, and time zone information for a zip code. The JSON and XML responses will allow contain alternative acceptable city names for a location. Send a GET request to https://www.zipcodeapi.com/rest/<api_key>/info.<format>/<zip_code>/<units>.

let URL := "https://www.zipcodeapi.com/rest/" + API_KEY  + "/info.json/" + Zip + "/degrees";
let response := http("GET", URL);
City := response.result.city;
State := response.result.state

slowwaggon's solution is better for auto updates.

I grabbed a zipcode DB from here.

https://simplemaps.com/data/us-zips

I imported the csv and created a new table. I took the defaults except for zip I changed from a Number to Text so it would keep leading zeros.

let myCustomer := this;
City := text((select uszipsv1)[zip = myCustomer.Zip].city);
State := text((select uszipsv1)[zip = myCustomer.Zip].state_name)