Invite outgoing call with third party softphone

Hello Martin. 
 
Thank you for contacting the Zendesk Support Advocacy team.  
 
Inviting an outgoing call with a third-party softphone application instead of using the integrated Zendesk Talk could be achieved, but it depends on the capabilities of the third-party application and how Zendesk is configured in your environment. 
 
I would recommend opening a ticket with our Support Team if you decide to do this integration, you can open a ticket if you have any queries. 
 
Please do let us if you may have further queries. 
 
Kind Regards