Can I integrate more than one Zoho Books/Zoho Invoice organization with one Zoho CRM account?

You can integrate one Zoho Invoice organization with Zoho CRM using two way sync and you can integrate other Zoho Invoice organizations using one way sync.

In order to setup the one way sync for another organization, kindly write to support[at]zohoinvoice[dot]com and we will enable this option from our end.