This phrase is mostly commonly found at the end of every broadcast of "The Daily Show", with Jon Stewart saying the tag line after the last commercial break, and throwing up a short video clip before the end credits.
A moment of Zen is something which inspires in the same reaction as does contemplating Zen koans does.
In Zen practice, deliberately irrational statements are sometimes used in Zen to jar persons into realizing the limits of the common uses of the intellect. One well-known example is, “What is the sound of one hand clapping?”.
Either of these instances can be applied to Jon's "moment of Zen", which often depicts political figures making fools of themselves, or satirizing the American public in general, so the epiphany can come from the realization of the satire, or the realization of how some people are just really, really stupid.
"Here it is folks, your moment of Zen!"
(clip appears onscreen of Italian Prime Minister talking about "bunga-bunga
" parties, and the news correspondant realizing he means orgies)