To change the DNS settings on your Windows 10 device using Control Panel, do the following:
On the left pane, click on Change adapter settings
Right-click the network interface connected to the internet, and select Properties.
Click the properties button
Type your preferred and alternate DNS server addresses.
Access ZYXEL P-660 H ADSL Router with default IP address "192.168.1.1" in address bar and click enter give password as "1234" and click enter
Click on "Network"
Click WAN -> LAN -> DHCP
Type your preferred and alternate DNS server addresses and click "Apply"
Login into D-link 2730 u ADSL router with default IP address "192.168.1.1"
Go to Advance and click on DNS
Specify the DNS server IP address highlighted box as below