I recently had to help a friend set up a Zoom X6 ADSL modem router and had a few initial problems connecting to the web interface. The main problem turned out to be that the inbuilt DHCP server is turned off by default.
The default IP address for the Zoom X6 ADSL modem router is 10.0.0.2
Although it does have a built in DHCP server this doesn’t seem to be on by default so you will need to set the IP address the computer you use to connect manually to something in the same range (10.0.0.3 for example).
The default user name is admin and password is zoomadsl.