To reset your router to factory settings, you can either use the on the device or the web admin interface if you still have access to your login credentials . Method 1: Use the Physical Reset Button (Hard Reset)
Performing a factory reset on the ZTE F668 will erase every custom configuration you have made. This includes your Wi-Fi name (SSID), Wi-Fi password, port forwarding rules, parental controls, and ISP-specific VLAN settings. In most cases, after a reset, the device reverts to default login credentials. How to Reset Factory Settings on ZTE F668