"Nobody on earth deserves such suffering," he said in the 30-minute emotional interview during which he broke down in tears at one point.
Zakka, an information technology expert, was arrested in Iran in September 2015 while trying to fly out of Tehran. He had just attended a conference there at the invitation of one of the country's vice presidents. The following year, he was sentenced to 10 years in prison in a closed-door trial after authorities accused him of being an American spy — allegations he and his associates vigorously reject.
He was released Tuesday and flew back to his native Lebanon, amid heightened tensions between the U.S. and Iran. Last year, the Trump administration decided to withdraw from the 2015 nuclear deal and re-impose heavy sanctions on Iran. The past weeks have witnessed a flurry of diplomatic activity to ease tensions and salvage the landmark deal.
Zakka is one of several prisoners with either dual nationality or links to the West held in the Islamic Republic's prisons. It was not clear why Iran decided to act now, after years of Lebanese officials asking for his release. The White House said it was "thankful" for Zakka's release but wants to see other Americans who are detained there released as well.
"In my opinion, it was a good timing for the Iranians, and especially they had a request from the President of the Lebanese Republic," Zakka told the AP. "They took this opportunity to send also a message ... de-escalating tensions within the region."
Zakka said that during his detention he met several Westerners held in Iran, and for two years shared a cell with Chinese-American Xiyue Wang, a Princeton University graduate student sentenced to 10 years behind bars after being accused of "infiltrating" the country and sending confidential material abroad.
He said Wang suffered from a skin disease and it took prison authorities months to get him medication. "I really ask President Trump to not leave Xiyue behind and other Americans behind, please," he said.
Wang's wife, Hua Qu expressed in an email her happiness for Zakka's release adding: "I welcome any help to free Xiyue who was also sentenced to 10 years and I keep praying for the day when our families can welcome him to Beijing and give him a hug with our son Shaofan, who has lived half of his life without his father."
Zakka also said Nazanin Zaghari-Ratcliffe, an Iranian-British woman, was held in the same building where he was until she was moved to the women's section inside Evin prison. She is currently serving a five-year prison sentence for allegedly planning the "soft toppling" of Iran's government while traveling with her young daughter.
Zakka added that Iranian-American Siamak Namazi was held in a cell "almost two meters away" from his, while the man's octogenarian father Baquer Namazi, a former representative for the U.N. children's agency UNICEF, was held on a floor above. Both father and son are serving a 10-year sentence after they were convicted of collaborating with a hostile power. He said he had also been held with Iranian-American art dealer Karan Vafadari and that his Iranian wife, Afarin Neyssari, was held with Zaghari-Ratcliffe. The couple are serving 27-year and 16-year prison sentences, respectively.
Asked whether he met former FBI agent Robert Levinson, who vanished in Iran in 2007 while on an unauthorized CIA mission, Zakka said: "We heard some stories. Some people told me that they saw him. It wasn't confirmed stories."
Levinson's family said in an emailed statement to the AP that Zakka's statement "further confirms that Iranian authorities kidnapped our father, continuously lied about it, denied him every basic universal human right, and have been getting away with it for more than 12 years."
The family called on the Iranian government to "send Robert Levinson home now."
Zakka said he made a promise to the detainees in Evin that he would not leave them behind.
"Please I ask again, please do everything possible to get them back home. I ask president trump please do everything possible to get these people back home."
Zakka, 52, described how he was detained as he was headed to the airport in a taxi on Sept. 18, 2015 after a visit to Iran following an invitation by one of its vice presidents. "I was stopped by a civilian car and taken by people in civilian clothes. They took me as a hostage since then. I didn't know anything. They blindfolded me and they took me to a place for almost 40 days. I didn't know where I am."
He added that the men told him that they are members of the intelligence department of the Revolutionary Guard, and that they control the country.
"We decide. We are the judge. We are everything," he recalled them saying.
When the time came for his release, Zakka said he couldn't believe it.
On Tuesday, after his release, Zakka said he was taken by officers to shops in Tehran where authorities insisted he choose a carpet as a gift, while cameras were filming. He was then taken to the presidential pavilion at the airport and received "like a guest of honor."
"Everybody was saying sorry for what happened, and I went to the plane."
Associated Press writers Zeina Karam in Beirut and Jon Gambrell in Dubai contributed reporting.