The "x" and "y" in that link don't refer to latitude and longitude, but rather an alternative coordinate system based on integer "tile numbers." For example, a zoomed-out map of part of South America has x=10, y=15, and zoom=12:

http://mt0.google.com/mt?n=404&v=w2....0&y=15&zoom=12

This URL is for topographical maps. The other URL is for street maps.

Use the "Download by Area" or "Download Along Route" menu items in the "Maps" menu of Maemo Mapper, or use a third-party program.