Combine crushed crackers, 1/4 cup of the sugar, and 2 tablespoons flour. Stir in butter. Press onto bottom and 1-1/2 inches up sides of ungreased 9-inch springform pan. Bake in the preheated oven 8 minutes; set aside.
Increase oven temperature to 375 degrees F. For filling, in a large mixing bowl beat the cream cheese for 30 seconds. Add the remaining 1 cup sugar and 2 tablespoons flour; beat well. Add egg product or eggs and vanilla. Beat on low speed just until combined. Stir in orange peel.
Pour filling into crust-lined pan. Place in a shallow baking pan in the 375 degree F oven. Bake 45 to 50 minutes or until center appears nearly set when gently shaken. Cool in springform pan on a wire rack for 15 minutes. Loosen crust from sides of pan with a thin-bladed knife or narrow spatula and cool 30 minutes more. Remove sides of pan; cool 1 hour. Cover and chill at least 4 hours or up to 24 hours.
To serve, drizzle melted marmalade over cheesecake. Cook and stir chocolate pieces and shortening in a heavy small saucepan over low heat until melted. Drizzle chocolate mixture over cheesecake. Makes 16 servings.