Complex sentence: Mannix appeared in the film version of Florenz Ziegfeld's life, "The Great Ziegfeld" (1936), and met MGM studio manager E.J. "Eddie" Mannix, and lived with him as mistress and later as his wife until his death in 1963.
Split into simpler sentences: Mannix appeared in the film version of Florenz Ziegfeld's life, "The Great Ziegfeld" (1936), and met MGM studio manager E.J. "Eddie" Mannix. She lived with him as mistress, and then as his wife, until his death in 1963.