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1
Preheat oven to 350 degrees F (175 degrees C). Grease and flour three 8-inch round cake pans.
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2
Mix sugar, all-purpose flour, whole wheat flour, cinnamon, salt, and baking soda in a bowl.
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3
Combine oil, eggs, carrots, and zucchini in a large bowl; beat with an electric mixer on low speed until well blended. Beat in honey. Stir in sugar mixture gradually; beat on medium speed until batter is smooth, about 3 minutes.
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4
Divide batter evenly among prepared cake pans.
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5
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 30 minutes. Cool in the pans for 5 minutes. Invert onto a wire rack; allow to cool completely, about 25 minutes.
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6
Combine confectioners' sugar, pineapple, cream cheese, walnuts, butter, and vanilla extract in a large bowl; beat until frosting is smooth. Spread over cooled cakes and stack.
