I just unranked to middle position. Preheat oven to 350°
Process graham crackers in food processor until finally crumbled. Add butter; process until blended. Pat crumbs over bottom and 1 1/2 inches up sides of a 9 inch spring form pan. Place on baking sheet; bake 10 minutes until golden. Cool completely.
Beat cream cheese and condensed milk at medium speed in bowl of electric mixer until smooth. Add ricotta, vanilla, and orange zest; beat until smooth. Add eggs one at a time, beating well after each addition.
Pour mixture into cooled crust. Bake 50 minutes until cheesecake is puffed and golden & a tester inserted 1" from center comes out clean. Cool on wire rack 35 minutes. Cover and chill at least two hours. Serve at room temperature.