Opening one app inside another - Not Deeplinking

I’ll define my problem statement - I have an account opening part of the application that was developed entirely by a different team in the form of an application. This part is an app all by itself - it has it’s own routing, theme, etc. Now we have a parent application which is developed by another team and this also is an app by itself. I want to open the account opening application inside this parent application on a button click of create account. How can this be achieved? Please help as dumping the entire codebase into parent app will be very unclean architecture.