Question: how to change username and password on zyxel router?
Answer: First, you will need to log in via IP Address. To do this, open any browser and navigate to 192.168. ... 
Select the Settings/Configuration icon (two gears) on the left side of the screen. Then, select Wireless Settings LAN 2.4G.
In Wireless Settings LAN 2.4G, enter your desired username in the Name (SSID) field.