Using advanced custom fields from one custom post type in another custom post type / using nested shortcodes

I think that, as you are using a Relationship model in your ACF settings, you have to iterate through the elements on your page.
For that reason, you can simply use the code from the ACF docs, and add it to your single.php or page.php.
https://www.advancedcustomfields.com/resources/relationship/

If you still want to use shortcodes, you can create an own shortcode including the sample code from the link above.

Hope this helps!