Walton, who announced in July that he would depart at the end of the year, has presided over the company from its headquarters in Atlanta. Zucker will continue to live in New York.
Flint predicted that would mean Zucker spending "half his time on a corporate jet instead of being in the trenches with the team that so desperately needs a leader."
Flint also questioned whether Zucker would see CNN as a stepping stone to a higher position, and be focused on a "next land grab."
Kent said Thursday that Zucker's overseeing CNN from New York will be no obstacle at all, and noted that many CNN/U.S. programs originate from New York.
And Zucker said he looks forward to reporting to Kent.
Andrew Kirell, on the blog Mediaite, said in an October article that while Zucker's coming to CNN would likely stir controversy among his critics, his "failures" at NBC were "far more widely covered than his enormous success in leading NBC's cable assets -- a record which would be directly relevant to the CNN job. On the news side, he can be largely credited with guiding MSNBC out of the gutter and establishing it as an actual competitor to Fox and ultimately beating CNN."
Zucker will supervise the heads of CNN's various divisions, including CNN/U.S., HLN, CNN International and CNN.com.
His entry into the Time Warner corporate family is sure to create a stir for media watchers for another reason -- one that has nothing to do with TV news.
Conan O'Brien has a show on TBS, CNN's corporate cousin. Zucker famously evicted O'Brien from NBC's 11:35 p.m. slot after just seven months hosting the "Tonight Show."
While it could make for an awkward moment at Zucker's welcome party, the O'Brien saga -- which involved removing, then restoring, Jay Leno to the time slot -- also highlights what is at times one of Zucker's strengths: a willingness to think outside the box.
"I do think that taking a risk and trying something new is something that we should always be willing to do," he once told CNBC.
Zucker has a publicly avowed fan in Piers Morgan, who hosts a primetime CNN program. "I love Jeff Zucker. I wouldn't be here without him," Morgan recently told The Hollywood Reporter.
Morgan was under contract with NBC's "America's Got Talent" when he got the CNN offer.
"Everybody had said to him, 'Don't let him go,' and, 'Why do we want to share our talent with CNN?' And he said, 'I get it. This is your dream job, and I'm going to let you do it,'" Morgan said, adding that Zucker is "a very capable executive."
Zucker became executive producer of "Today" at the age of 26, in 1992.
"I worked really hard through a very tumultuous time at the 'Today' show," Zucker said in a talk posted on YouTube this year by IMG Speakers.
"Under his leadership at 'Today,' the program was the nation's most-watched morning news show and the most profitable program on television," says Zucker's official biography on the GE website, from his days at NBC. "Zucker has also served as executive producer of NBC's coverage of several major events, including the 'Decision 2000' election night broadcast, the 1993 and 1997 presidential inaugurations and the Persian Gulf War."
In 2000, Zucker was named president of NBC Entertainment. He then rose through the ranks, becoming president of the network's Entertainment, News & Cable Group and, in 2005, CEO of the NBC Universal Television Group.
As NBC's ratings fell, many critics blamed Zucker, with some chalking it up to his record developing sitcoms.
Still, in 2007, Zucker was again promoted, becoming CEO of NBC Universal.
Zucker left NBC in 2010, after the company merged with Comcast.
He launched Katie Couric's talk show this fall. Entertainment Weekly reported in October that the program was among the new talk shows "leading" in the ratings, but The Hollywood Reporter said "Couric's middling ratings and topics" had "affiliates grumbling."
A Harvard graduate, Zucker showed an interest in journalism during his college years. He was editor of the Crimson, the school's daily newspaper.
O'Brien at the time ran the Lampoon, the school's humor magazine -- and Zucker once had O'Brien arrested over a prank.
"Zucker is one of the most competitive guys you'll ever meet," Fortune writer Patricia Sellers said in 2010.