With your Zenmate client already installed, please double click the ZenDesk icon on your desktop to start the ZenMate software.
Once the ZenMate software is opened, click on the 'Expand' menu - located on the left side of the app:
With the Expanded view of ZenMate, head to the Settings menu:
With the Settings menu opened, open the Connection tab:
From the VPN Protocol drop-down menu, choose OpenVPN instead of Automatic Selection:
After OpenVPN is selected from the drop-down menu, please close ZenMate from the systray simply right-clicking the ZenMate icon and choose: Exit:
Now, ZenMate can be started again and now, your connections will now run via OpenVPN.