It doesn't appear the three forces are all pointed against the Iranian government. Democracy is certainly working against the regime, but is religion? It's unclear. Iranians don't like theocracy, but they are religious, and clearly (President Mahmoud) Ahmadinejad got the votes of the more rural and observant masses. As for nationalism, neither side can truly claim it.
Again, like Taheri, Zakaria claims he knows about Iran, when he statements are assumptions. The people of Iran put Nowrooz above Islam, and he should know that. Finally the reason that Mr Mousavi had so many people with him, was that the nationalists came out and voted for him.