No, it is not possible to synchronize several Cozy with a computer, or at least not simply.
Cozy is a personal server, to centralize all your digital life, both personal and professional.
The synchronization application was therefore designed to be able to connect to only one Cozy account.
Allowing synchronization with several Cozy would require a major overhaul of the way the application works, that is not planned.
But if several people use the same computer, each with a separate local account, each local account can be synchronized with a separate Cozy.