How do I sync the invoices created in the native module of Zoho CRM to Zoho Books?

There is no direct sync between the Zoho CRM’s native modules (including Invoices, Quote, Sales Orders, and Purchase Orders) and the respective transaction modules in Zoho Books. However this can be achieved using a Custom Function. You can write to support@zohocrm.com for further assistance in this regard.

Learn more about custom functions.