We have recently completed data migration in ZOHO Projects for a client. We have migrated from one ZOHO acct to another - and migrated all projects data including tasks, subtasks, attachments, timesheets etc. And associated the projects with CRM records. Over 1000 projects, and 35K attachments. 

Note: ZOHO backend migration support is only for projects, tasks and does not include attachments, timesheets, or support projects association in CRM etc.

For those of you looking for migration related assistance, please reach out to us : ask (at) upwise (dot) pro for more details.