It is not possible to edit favorites. However, you have to delete and re-assign a new contact after you refreshed the downloaded phonebook on your ZENEC device.
Your smartphone contacts will only be downloaded after your confirmation during the first connection after search&pair. Any later changes made to your contacts must be refreshed by a manual download …
Usually the device will generate a 6-digit code automatically, which then needs to be confirmed. In case you have to manually enter a PIN code, try four times zero (0000).