This would depend on if the other plugin allows you to modify the templates that it uses. If the templates can be modified, or if they provide hooks that let you add content to the templates, then you could potentially add an acf_form() https://www.advancedcustomfields.com/resources/acf_form/ inside of the existing form created by that plugin with the 'form' options set to false.
You’d need to find out from the developers of the other plugin if it’s possible to add fields inside of their form and to modify the header output to include the call to acf_form_head()
