+a) Does CP supports Private Zone?+

Yes, CPBM supports the CloudStack concept of Private Zones.

b) If yes, what is the behaviour when there are private zones?

A customer end user will see the private zone in the CPBM UI – as part of the catalog, launch VM, service health - if their company has been provisioned by CPBM under the CS domain that has a mapping to that private zone.

If there is a private zone mapped to a domain that has been created directly in CS (out of band of CPBM) then that private zone is NOT surfaced up in CP.

c) Who can view these private zone?

Only those CPBM customer accounts whose corresponding CS domains have been mapped to that private zone(s).