You question is just a variant of this question and demo which created three records in different tables with one form:
Creating 2 records (in two different apps) using only 1 formhttps://community.quickbase.com/quickbase/topics/creating-2-records-in-two-different-apps-using-only...
The Triplicate Forms demo created identical copies of the record in two other tables (three total). The script used the FormData API with the Fetch API (the replacement for XHR). All you have to do is modify which of the original form fields needs to be included in the FormData sent to each of the tables when posting the FormData.
See this documentation:
MDN FormData APIhttps://developer.mozilla.org/en-US/docs/Web/API/FormData
If you need individual assistance implementing this solution feel free to contact me off-world using the information in my profile: