How to have in zoho invoices, every timesheets, client and projects that we had created in zoho project? (and/or vice versa)

In Zproject, I can create a client, and in Zinvoices too, so why can’t I find those client in both apps when I create one? And it’s the same for timesheets and projects.

For instance, right now we can export timesheets of Zproject but we can’t import them  directly   in Zinvoice because it’s not the same data disposal in the template of export/import.

Thank for your help !