Theory
Life
Let's take apart this equation. What is 6? It is widely accepted that six is representative of pure evil (the number of the beast, etc.). Seven, on the other hand, is representative of perfect good. So, while 6 x 7 = 42 and 42 is the Ultimate Answer, it is also the balance between good and evil.
the Universe
If you take the number 6, and draw it four times with the round parts overlapping, you make the symbol of a spiral galaxy. If you take the number 7 and draw it four times with each 7 mirroring the other, you make a time cone. This comes to the balance between space and time.
Everything
If you take the time cone formed by the 7s from the Universe equation and turn it on its side, it resebles infinity. You take two sixes and draw them conjoined, they also form infinity. Infinity times infinity = infinity and infinity encompasses everything!
"It's like having your brains smashed out with a piece of lemon wrapped around a golden brick." -The Hitchhiker's Guide to the Galaxy