If you want to change advanced settings (VLAN, bridge mode, TR-069), you need the super user. The standard "user/user" only gives you basic Wi-Fi changes.
Type the default IP address into the browser's address bar and press Enter. For the ZTE F663NV3A, the default IP is typically: 192.168.1.1 or 192.168.0.1 password zte f663nv3a exclusive
If the tier 1 passwords fail, your ISP has locked down the admin account but left the engineering account open. These give you the same power. If you want to change advanced settings (VLAN,
The Definitive Guide to the ZTE F663NV3A Exclusive Password and Administrator Access password zte f663nv3a exclusive