Hello,
The solution for your project is by using the integration of API for Zoho part and SDK for Sage 50 Cloud. There is no API for the Sage 50 Cloud, so you will need an intermediate apps which will bridge the data flow between Zoho and Sage 50 Cloud. I will write the code for this intermediate apps and this should be executed on either your desktop or server as well. The process can be set as the scheduled based, e.g.: per minutes or any other certain intervals.
Let me know if this method is feasible for you.
Best Regards,
Khamid