Doing a bit more Googling, I think this guy is lying his ass off.
In his recent claims, he does not tie Iran directly with 9/11. However he says, according to the LA Times:
The Iranian witness also said he had seen Ziad Samir Jarrah, the Lebanese hijacker believed to have flown the United Airlines jet that crashed in Pennsylvania, at a Hezbollah training camp near Tehran in 1997, the sources said. Hezbollah and its operational chief, Imad Mughniyah, have long been supported by Iran.
http://www.latimes.com/news/nationworld/world/la-fg-terror22jan22,1,6714857.story?coll=la-headlines-worldThat in and of itself sounds extremely dubious. But this isn't the first time he's come forth with his story. There's an article from June 2003 in the right wing, Moonie owned Washington Times (their magazine, Insight):
http://www.insightmag.com/news/2003/06/24/World/Defector.Alleges.Iranian.Involvement.In.Sept.11.Attacks-438491.shtmlIn that, he goes totally overboard in envisioning Iran being behind the attacks:
The talks with al-Zawahiri went so well that bin Laden dispatched his eldest son, Saad bin Laden, on a return trip to Iran exactly four months and seven days before Sept. 11, according to Zakeri. The younger bin Laden was flown from the Tayebat border crossing with Afghanistan to the Damavand air base outside Tehran. "He came with three other people," Zakeri says. "They were not introduced to me and spoke Arabic amongst themselves. But Saad spoke good English." Zakeri says he stayed in Iran for three weeks but held just one official meeting, which took place at 3 a.m. at Khomeini's former meeting house in Jamaran, on the slopes of the Elburz Mountains in Tehran's northern suburbs. Present were all five members of the Leadership Council, Zakeri says: Khameini, former president Hashemi Rafsanjani and ayatollahs Mohammad Yazdi, Mahdavi Kani and Ali Meshkini.
It was at that meeting, on May 4, 2001, that final plans for the attack on the U.S. mainland were made, Zakeri believes. Shortly afterward, he recalls seeing a striking exhibit in the entry hall to the main headquarters of the MOIS in Tehran. "It was a model of the World Trade Center, the White House, the Pentagon and Camp David," he says. "From the ceiling, a missile was suspended, as if to strike the buildings. 'Death to America' was written on its side in Arabic, not Farsi."
---
There's a lot more like that in the Insight story. He claims the entire al-Qaeda leadership travelled as a group to Iran in early 2001 to discuss the 9/11 plot. Riiiiight.
The fact that his recent claims apparently completely fail to mention this stuff says to me this guy is a complete BS artist.
The Insight article also says this:
A U.S. intelligence official categorically denied that Zakeri had delivered such a warning. "We have no record that he made such a claim. He is a fabricator of monumental proportion."