That doesn't appear to be a real quote from Brzezinski. Nobody can find the original source of him saying that. It appears to be what somebody writing about one of his books claims is a quote from the book, but it doesn't actually appear there. Might be a paraphrase.

Apparently Metabunk is a banned domain.
https://web.archive.org/web/20171108230334/https://www.metabunk.org/%E2%80%9Cshortly-the-public-will-be-unable-to-reason-or-think-for-themselves-%E2%80%9D-%E2%80%94-zbigniew-brzezinski.t9138/

Here's the info I can't link to

It's probably a paraphrasing of something in Between Two Ages. Here's a 2009 reference, seemingly an interview with Steven Jacobson. https://web.archive.org/web/20090831173245/http://pupaganda.com/originals/Tv_mind_control.html