Regarding the CLI credentials. CLI login credentials are different from the GUI ones.
Usually, when setting the SZ for the first time using the GUI wizard, the system asks for a user and password, at this moment the credentials you entered are the same for GUI and CLI access.
Later, usually the admin changes this credentials using the GUI, but the credentials only changes for the GUI access, the CLI remains the same, the ones you entered when doing the wizard. So, if you haven't access CLI since the beginning, probably the CLI login credentials are the ones you entered for the first time.
CLI admin password can only be changed from the CLI itself.
Hope this helps in any way.