While restoring a Zerto backup using Zerto is best because all the VM settings are restored along with the virtual disks, is it possible to mount the Zerto backup repository into VMware or Hyper-V and then create/register a virtual disk using the “data.vol” that is produced during the Zerto backup?? In other words, are the virtual disk image files created during a Zerto backup usable without Zerto?
You need to have ZVR in order to use the data replicated by ZVR.
The portability described is closer to the Zerto Offsite Backup feature. It was designed to give you the ability to protect entire VPGs. Offsite Backup creates a portable package that is transportable via file copy. However, you still need a ZVM to reconstitute the Offsite Backup.
More on Offsite Backups here: http://s3.amazonaws.com/zertodownload_docs/Latest/Zerto%20Virtual%20Replication%20Zerto%20Virtual%20Manager%20%28ZVM%29%20-%20vSphere%20Online%20Help/index.html#page/AdministratorforZertoVirtualManager%2FInitialConfiguration_VC.02.6.html