The three sheets of papers taped to a window, spelling ZAC, give little indication of the growing temple housed in a former church on Walnut Avenue.

The Zoroastrian Association of California Center, or the ZAC Center, has been the group’s home since 2010, a community center in which the 400 members can pray, meet and celebrate.

“It’s growing day by day,” said Mitra Irani, a member of the association since the 1980s.

Zoroastrianism, one of the oldest monotheistic religions in the world, is an ancient Persian religion that emphasizes peace and nature. There are an estimated 2.6million adherents in the world.

The religion was founded in the 6th century BC by Zarathushtra, also known as Zoroaster. The religion believes in one god, Ahura Mazda, and that there are opposing forces of good and evil in the world.

“The core religion is good thoughts, good words and good deeds,” said Tehmi Damania, the Southern California association’s president.

The association was founded in 1974. Its members come from as far south as San Diego and as far north as Calabasas. Prior to buying the vacant church in 2010, the group was nomadic, Damania said, renting various community halls for its services and events.

From Orange County, the bulk of the membership comes from Irvine, Damania said. But the group chose to locate in Orange for the two reasons: it was difficult to find property in Irvine, and Orange was more central to the spread-out membership.

“I walked in and could feel … I felt right then that this is it,” Damania said of when the group found the Orange spot, just east of First Christian Church of Orange and Orange Seventh-day Adventist Church. They bought the 2-acre property for $2.6million.

Most of the association’s members are Parsi – Zoroastrians whose ancestors landed in India after being exiled from Persia. There are about 70,000 Parsis in the world.

In Orange County, there is also a Zoroastrian center in Westminster, called the California Zoroastrian Center. Most of its members are Iranian.

The ZAC Center holds services every Sunday. Because of the spread-out membership, typically only about 50 people come, and the service is conducted as group prayer in a small room called the Hong Kong Room, after a $250,000 donation from the Zoroastrian community in Hong Kong.

For bigger gatherings, the center has a community hall. The room is adorned with various pictures of Zoroaster and other prophets of the religion. At the center above the stage is a picture depicting the religion’s founding that includes an image of the eternal flame, an element most Zoroastrian temples include but which the center lacks.

One large event that will be held in the hall is the upcoming celebration of Navroze, the Persian New Year. About 200 people will come for a prayer ceremony, called jashan, and led by a priest, followed by singing, dancing and feasting. The holiday is March 21, the day after the spring equinox.

“Spring is when everything starts growing,” Damania said. Then she joked, “Everything centers on food.”

Contact the writer: 714-704-3771 or rkheel@ocregister.com