Former ambassador Andrew Young, an official representative of President Carter at the Zimbabwe independence celebrations, met here today with officials of the Palestine Liberation Organization.

Young, who resigned under fire in August as U.S. ambassador to the United Nations after Israel protested against talks he held with a PLO representative, said his 35-minute session today was strictly informal and not part of his official mission. The United States has refused to have official dealings with the PLO until it recognizes the existence of Israel. o

The meeting was one of scores held between a wide variety of world leaders gathered here to honor the birth of Zimbabwe and the installation of Robert Mugabe as prime minister. Celebrations were held throughout the country today as the nation began a two-day holiday.

Another major meeting brought together Indian Prime Minister Indira Gandhi and Pakistani President Mohammad Zia ul-Haq together for the first time to discuss problems between the two nations that have fought one war and still have rocky relations.

Both leaders described their 55-minute session in positive terms and indicated that there would be further talks.

Young said that in his meeting, Hani Shawwa, the PLO representative in Mozambique, and Gamal Sourani, a PLO representative from Syria, simply repeated familiar Palestinian arguments against the Camp David agreement. Young said he replied that the Camp David formula, which has produced peace between Israel and Egypt but is bogged down over the issue of Palestinian autonomy, was the only road to follow.

The controversial former ambassador said the talks -- his first with the PLO since he left office -- were coincidental, occurring only because he ran into the representatives in their hotel.

Young said the gathering of officials for Zimbabwe's independence provided a good opportunity for impromptu talks.

He said he had seen a "nice collection of liberation movements." These included the Montoneros from Argentina; the Polisario Front, which is fighting to wrest control of the western Sahara from Morroco; and Fretilin, which is seeking independence from Indonesia for the island of West Irian.

Assistant Secretary of State Richard Moose Jr. also sought to downplay the PLO meeting saying: "You know Andy. He sees somebody, he talks to them."

In the Gandhi-Zia meeting, the Indian prime minister softened her government's previous opposition to the United States' offer to provide Pakistan with arms because of the Soviet invasion of Afghanistan.

"We talked about Pakistan's military needs and we understand their position better now," she said.

Zia called it "an honor" to meet Gandhi and said the talks will contribute "to a better relationship between India and Pakistan which we are in need of at this time."

Dozens of foreign officials sought to see Mugabe today but most of his time was taken up by three independence rallies, the lighting of an eternal flame to honor those killed in the seven-year war that led to independence, and an interdenominational prayer service.

Mugabe also said farewell to Prince Charles, who represented Britain's Queen Elizabeth at the independence celebrations and to Lord Soames, the British governor who took power last December to end Rhodesia's illegal status. Soames guided the restored colony through a transition period leading to the election of Mugabe's government.

The United States rushed to establish relations with the new government, becoming the first country to officially open its embassy. Young presided over a ceremony in which the United States agreed to provide $2 million for rehabilitation of 160 provincial health centers as the "first installent" of $15 million of aid promised for this fiscal year.

The new health minister, Herbert Ushewokunze, praised the aid and, like Mugabe in recent days, made it clear that the country will need considerable outside help to rebuild the country.