I have created an "External Contacts" Custom Module for adding Contacts who aren't directly associated with a Customer or Vendor but who are related to Orders by being a Site Contact, Job Contact, Warehouse Contact, etc for third party.

How can I go about achieving a workflow to add these Contacts to a Sales Order, Purchase Order or Customer?  Zoho Books doesn't allow lookups to Custom Modules from Standard Modules.

Would a Zoho Flow ZBooks-ZBooks integration provide access to the module as an External Lookup?