One email address cannot be used with two similar product models.
Example: You cannot use two ZeTime with the same email address.
One email address can be used with two different product models.
Example: You can use the same email address to create an account for ZeTime and ZeRound2
Note: If you want to pair your ZeTime with another account or smartphone, you first need to unpair from the current one. On the mobile app, go to Settings > click on Unpair ZeTime.
Then, perform the pairing procedure, see How do I Set Up my ZeTime?.