Yes. Zentrunk SIP URI can be used to make calls from any soft phone. To achieve this, create an account on a soft phone (say X-Lite) uncheck “Register with domain and receive calls” under account preference.
Here are two tutorials that walk you through how to configure your soft phone (e.g., X-Lite) and soft switch (e.g., FreeSWITCH or Asterisk) to work with your Zentrunk SIP endpoint.
Zentrunk & FreeSWITCH configuration Zentrunk & Asterisk configuration