Please automate mail merging of document via workflow

Please automate mail merging of document via workflow

I have several documents that use information from a subform in a Deal or Custom module. That information needs to be sent to clients and staff at certain times or on a field update. 
I can create a workflow in CRM, but cannot access subform info in the email templates associated with workflow emails. 
I can create a mail merge document in Zoho Writer, but cannot automate the process of sending this document. 
HOW do I combine both of these functions in one process???? This is so vital to our business, and not having this impacts our impression of Zoho's usefulness. 
Please help. Thanks!!