The source you’re looking for is Zohar Chelek 3 Daf ayin alef, amud beis.
“Tzadikim are found more in all worlds after their passing, as during their life they are only found in one world, whereas after their passing they are found in all the worlds.”
And further toward the end of the daf:
“Tzadikim in their life defend the world, and even more so after their passing”
“Without the prayers of Tzadikim the world wouldn’t be able to stand for even one moment.”
@grass,
My Rebbe taught me that when one knows alef they should teach alef. That would seem to imply that when one doesn’t know beis they shouldn’t be teaching beis. Respectfully, your comments above are like someone who doesn’t know alef trying to say they know tuf.