Multiple users for Zoho CRM and invoicing

Multiple users for Zoho CRM and invoicing

Confused about ZohoCRM and streamlining the invoice process.
So here I am using zCRM and I'm ready to create an invoice.  But which route to go?
I can create the invoice in zCRM, zInvoice, or zBooks.  Which route is best?

I would like to use Zoho for running a small service based business and each team-member (employee) having their own zCRM to maintain their own clients.  Each team-member should also create and send out invoices.  

I have one main zCRM account and add each team-member as a user... seems like the right solution.  After adding each user I could set up roles and profiles so that each team-member only sees their own clients.

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BUT how do I get invoicing to work under this scenario?
Preferably each user should be able to create, edit, and send out their own invoices for their own clients.  

Do I purchase a separate zInvoice subscription per user?
Or do I purchase one zInvoice subscription and add everyone as a separate user?
Or does zBooks have better user management and would be better?

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