When the relatively moderate Mohammed Khatami was elected president in Iran, American conservatives pointed out that he was just a figurehead. Real power, they said (correctly), especially control of the military and police, was wielded by the unelected "Supreme Leader," Ayatollah Ali Khamenei. Now that Ahmadinejad is president, they claim his finger is on the button. (Oh wait, Iran doesn't have a nuclear button yet and won't for at least three to eight years, according to the CIA, by which point Ahmadinejad may not be president anymore. But these are just facts.)
Leaving aside quibbles about the reliability of the CIA's intelligence, the logical conclusion to draw from all this would be that the person you really need to worry about with regard to Iran is Khamenei, not Ahmadinejad.
Instead, though, Zakaria spends his column expounding on why Ahmadinejad is really not so bad, how Iran hasn't invaded anyone for over 200 years--which is SUCH a comfort when the actions we're worried about Iran taking don't involve invasion at all--and so forth.
I do agree that there's a tendency on the part of many to overemphasize the importance of Ahmadinejad in the overall picture.
Unfortunately, Zakaria took that valuable insight and ran with it...straight off a cliff.