A violent criminal on parole was charged with attempted murder for allegedly tossing an elderly woman onto Midtown subway tracks in a terrifying weekend attack, cops and sources said. Zaki Smith, 36, was picked up by eagle-eyed cops during the Monday evening rush and charged in connection to the 11:30 a.m. Saturday attack at the 57th Street and Seventh Avenue station that left the 70-year-old victim with a head wound, police said. Smith — who has 14 previous arrests — was also charged with felony and misdemeanor assault in the senseless shove, authorities said. Commuters who witnessed the attack heroically...