Beat cream cheese and remaining sugar in large bowl with mixer until blended. Add eggs, 1 at a time, mixing on low speed after each just until blended. Add liqueur and zest; mix well. Remove 2 cups batter; place in medium bowl. Add melted chocolate; mix well. Pour remaining batter over crust. Drop spoonfuls of chocolate batter over plain batter. Cut through batters with knife several times for marble effect.