You can try the following:
1. On ZS WebGUI go to Setup – Scripts/CRON
2. In the Scripting Editor click on the Add Job button on the lower right corner of the window.
3. It will prompt for a name for your script. Type a name like (VPNRestart) and click Ok.
This will create a new empty script.
4. On the script text dialog add the following line at the bottom:
/root/kerbynet.cgi/scripts/vpn_ctl VPN00 up
Please note that in the example we are going to start VPN00. Change it to reflect the VPN you need
5. At the bottom of the window you can set the schedule time for the script to execute.
6. Click on the Status checkbox to enable.
7. Click Save button to activate.