During the auto-sync, the most current version of an account's data is copied over to Zoho Invoice. So any changes or additions that are done in Zoho Invoice will be over-written. However, if the fields in which you had entered information are not available in Zoho CRM, like the custom fields; then they will not be over-written. Here's a list of fields that are over-written during the import.

• For accounts imported from Zoho CRM the following fields are over-written: Name, Billing Address, Phone, Fax, Shipping Address and the Notes
• For contacts associated with accounts: First Name, LastName, EmailID, Phone, MobilePhone
• For contacts that are not associated with any accounts, in addition to the fields mentioned above, the following fields are also imported: Mailing Address, Fax Number