Why do we need Zones when VSAN is good enough to logically segregate the fabric.
You would use VSAN's to keep Tape library in one VSAN and another for Windows servers or Dev Lab environment. To logically separate devices but if you need devices to talk between VSAN's then you would need IVR.
From within a VSAN you would use Zoning to put a Host and Storage Array in the same zone to provision storage just to that device (LUN masking). Zoning is like a direct mapping between a Host/s and Storage.
Hope that helps.