Lenses can get very confusing with all the different ways of saying what it is or does, but I'll try an explain. The 426mm refers to the length of the lens if it were on a 35mm film camera. Many makers give this equivalent length as a reference point for people because 35mm film cameras were the most common type in use until recently. The actual length of the lens varies according to the size of the sensor inside the camera, so for compact cameras it can be far less than 426mm and still be the equivalent of a 426mm long lens. The 12X zoom refers to the number of times the lenses shortest length is multiplied to get its longest length. So in this case 35.5mm. ( 35.5 X 12 = 426 ) The 35.5mm is an equivalent length too and the actual lens on the camera will not be 35.5mm long but much shorter. Hope this helps :)

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html