The present level of integration sports a one way sync of accounts and contacts from Zoho CRM to Zoho Invoice. Also, if you are on a paid subscription in Zoho CRM you will be able to view the invoices that are created for the synced accounts and contacts.

• Sign in to Zoho Invoice.
• Go to the Customers tab
• Click the "Import from Zoho CRM" link on the right hand side of the customers listing page.
• You will now be directed to a page where you need to enter your email address and Zoho Service Communication (ZSC) Key. If you don't have a ZSC key already, simply click the "Click here to generate ZSC Key link" to generate one instantaneously.
• Check the Auto-Update option, to enable the system to automatically sync the accounts and contacts data every 12 hours
• Click the Import button

If required, you can re-import the data at any time by following the instructions above. Please make sure that you update the "Accounts" and "Contacts" details only in Zoho CRM.

Check the Importing Zoho CRM accounts and contacts help section for more information