He's a process guy, not an ideologue. Zients comes from the world of management consulting, working at Mercer and Bain as a young man, then as a top lieutenant to David Bradley as he built the Advisory Board and Corporate Executive Board into large firms that advise businesses on how to run things better. Zients made millions when the two companies went public. He also played a key role trying to bring Major League Baseball back to Washington, working on the team of wealthy investors who hoped to land what would become the Washington Nationals. Their ownership group lost out to the Lerner family, but their efforts helped pave the way for the relocation of the team.
Zients joined the Obama administration to apply some of the same business know-how to government, initially becoming "chief performance officer" of the Office of Management and Budget. His job was to try to make government run better and push agencies to adopt best practices. He later served as deputy OMB director.
This background points to Zients being not an NEC director with strong views on economic theory, but one who keeps the policy process running well. He will likely be more Gene Sperling than Larry Summers, or to use the Bush administration parallel, more Al Hubbard than Larry Lindsey. (For a useful explanation of the NEC director job and how it interrelates with other economic policy officials, check out this 2010 explainer by Keith Hennessey, who also held the job under Bush).
He's a veteran of the Obama administration — but not a Clintonite. We have poked at President Obama for surrounding himself with economic policy advisers who share one direct intellectual lineage that goes back to the Clinton administration. Sperling, Summers, Treasury Secretary Jack Lew, OMB Director Sylvia Matthews Burwell, CEA chairman Jason Furman — they all served in various roles in the Clinton administration and have a line of mentors that goes back to Clinton Treasury Secretary Bob Rubin.
Zients is from outside that circle. He spent the 1990s building businesses, not serving in the Clinton administration. That said, he does continue the Obama administration's second-term pattern of promoting from within on its economic policy team rather than looking outside the walls of the White House compound.
His appointment doesn't help the administration's woman problem. Zients has been a respected player on the Obama team, but his appointment does not help the perception — and reality — that the president's economic advisers are predominantly male. At present, Burwell, the OMB director, is the only senior woman on the team (Sarah Bloom Raskin has been appointed deputy treasury secretary, but not confirmed).
Expect criticism on that front to only intensify if the president appoints Larry Summers Fed chairman instead of vice chair Janet Yellen, as appears likely to happen in the coming weeks.