HARARE, Zimbabwe — A new documentary on massacres by Zimbabwe's military … The screening in the capital, Harare, would have been almost impossible under former leader Robert Mugabe, who led the country for 37 years and resigned following military intervention in November. President Emmerson Mnangagwa, a longtime Mugabe loyalist and enforcer who succeeded him, has tolerated documentaries and plays critical of the government amid promises of a "flowering of democracy." But none has taken such direct aim at Mnangagwa as the new documentary on the army operation he supported as state security minister between 1983 and 1987. "Gukurahundi genocide: 36...