Albert J. Zack, 63, a former newspaperman who became a power in the American labor movement and the principal spokesman for the AFL-CIO until his retirement last year, died Wednesday at his home in Sarasota, Fla., after a heart attack. He lived in Sarasota and Washington.

Mr. Zack joined the ranks of labor by leading a 16-month strike against a newspaper in Springfield, Mass. In 1947, he went to work for the professional staff of the Congress of Industrial Organizations in Ohio. He was transferred to the CIO's Washington office in 1952. He rose to power as a member of the inner circle of George Meany, the late president of the AFL-CIO.

As director of public relations for the AFL-CIO, Mr. Zack was "the voice of George Meany" during most of Meany's 27-year presidency of the federation. As one of those closest to Meany, Mr. Zack helped formulate the same policies he advocated to the public, the Congress and the media.

As a spokesman for labor, Mr. Zack was regarded as tough and straightforward. Meany had implicit trust in his expertise in explaining labor's position. Reporters and officials were confident, in turn, that Mr. Zack was expressing Meany's views. These aspects of his career were stressed in a statement issued yesterday by AFL-CIO President Lane Kirkland and secretary-treasurer Thomas R. Donahue. They said:

"The high standards of truth and accuracy that made Al a news source of unquestioned reliability to generations of labor reporters brought honor to the federation he served, as well as to himself.

"The shock of Al's death has brought a deep and heartfelt feeling of sadness throughout this building in which he was so large and vital a presence for so many years. We know that the same grief will pervade union offices and newsrooms all across the land as word of his passing spreads."

Mr. Zack was born in Holyoke, Mass. He dropped out of high school and began working for newspapers. In 1942, he joined the Springfield (Mass.) Daily News as news editor. In 1946 and 1947, he led a 16-month strike against the Springfield newspapers.

After the strike ended, he went to Columbus, Ohio, and joined the Ohio CIO Council, where he was publicity director from 1947 until 1952. He also was executive secretary of the Columbus CIO Council, a post to which he was elected as a delegate from the Columbus Newspaper Guild.

He moved to Washington in 1952 when he became assistant publicity director at CIO headquarters. When the CIO merged with the American Federation of Labor in 1955, Mr. Zack retained that position. He was named director of public relations for the AFL-CIO in 1957. He retired on Jan. 11, 1980, the day after the death of George Meany. His final duties as director were the press arrangements for Meany's funeral.

Mr. Zack was a member of the National Press Club.

Survivors include his wife of 41 years, the former Jane Nesworthy, of Sarasota and Washington; a son, Allen Y., of Bowie; a daughter, Linda Tarr-Whelan of Arlington; a brother, Eugene, of Herndon; three sisters, Ruth Fuller of Norwell, Mass., Madeline Noll of West Haven, Conn., and Carol Bouchard of Enfield, Conn., and five grandchildren.