The ultimate question of life, the universe, and everything is indeed asking what is 6 multiplied by 9. (42 of course, as any well-read high school student could tell us.)
1) The ultimate question was 6 * 9 = ? and the universe makes no sense at all.
2) The ultimate question was 6 * 7 = ? and the universe has no deeper meaning.
Both are possible, and the ambiguity suggests he wanted to say both.