To get DNS-O-MATIC to work simply create a cronjob per steps below:
1.- In web interface of Zeroshell go to Setup
2.- Click on Startup/Cron
3.- At the bottom of the pop up window click “add job”
4.- Give the job a name.
5.- In the main Text Area paste the following code (replace password and username accordingly):
6.- Select the time intervals for running the job.
7.- DNS-O-MATIC should now be updating. You are good to go!!
DynDNS can then be set up through the Dynamic DNS settings in Zeroshell. Now you have both updating at once. Vuala!!!