Integrating freemium product customers sold on wordpress site to Zoho

Integrating freemium product customers sold on wordpress site to Zoho

We are trying to integrate our orders collected online via wordpress to zoho to manage our customers -- should our site talk directly to the zoho invoice module then our contacts go from there to the CRM or should the site talk to CRM and we import customers from there into the invoice module?  Just confused on how the CRM contacts talks to invoice ap contacts when all of our contacts are originating from our website.