A violent workers’ revolt at the world’s largest iPhone factory this week in central China is further scrambling Apple’s strained supply and highlighting how the country’s stringent zero-COVID policy is hurting global technology firms. The troubles started last month when workers left the factory campus in Zhengzhou, the capital of the central province of Henan, due to COVID fears. Short on staff, bonuses were offered to workers to return. But protests broke out this week when the newly hired staff said management had reneged on their promises. The workers, who clashed with security officers wearing hazmat suits, were eventually offered...