Using with Codeingiter 3

Hi,
we are using codeigniter 4 in a subfolder  for codigniter 3 project.
There are 2 different databases, one for project with CI3 and another for CI4. Also both databases communicate with each other.
We are able to to do everything, but I am looking for a possibility to load codenigter 4 models into codeigniter 3 controllers.


- Root Folder (codeigniter 3)
|_ application
|_ system
|_ index.php
|_ ci4 (codegniter 4)
|_ awesome (public folder, from ci4, renamed )