MIX crumbs, sugar and butter until well blended. Press mixture firmly onto bottom of 13x9-inch pan; set aside.
DISSOLVE dry gelatin mix in boiling water in large bowl; set aside. Place pumpkin, sweetened condensed milk, sour cream and cinnamon in blender; cover. Blend 1 min. or until smooth. Add to gelatin in bowl; mix with wire whisk until well blended. Pour mixture over prepared crust.
REFRIGERATE 2 hours or until set. Cut into 24 squares. Serve topped with whipped topping and orange zest. Refrigerate leftover dessert.