For the zucchini cake: Preheat the oven to 350 degrees F. Grease and flour two 9-inch round or 8-inch square cake pans, or one 13- by 9-inch rectangular cake pan.
Into a large mixing bowl, whisk together the flour, sugar, baking soda, baking powder and salt. In a separate small bowl, whisk together the vegetable oil, lemon zest and eggs. Using a rubber spatula, stir the egg mixture into the flour mixture until just combined. Fold in the shredded zucchini and chopped walnuts. Spread the cake batter evenly in the desired cake pans.
Bake until a toothpick inserted into the center comes out clean and the cake springs back slightly when touched and just pulls away from the side of the pan, 30 to 40 minutes.
Remove the cakes from the pans when completely cooled.
For the lemon glaze: Whisk together the confectioners' sugar, lemon juice and lemon zest until combined to the desired consistency.
To assemble: Brush the bottom cake layer with the lemon glaze and apply a layer of cream cheese icing. Top with the second layer and repeat with the glaze and icing. Top with toasted walnuts.
NotesThis recipe was provided by a chef, restaurant or culinary professional and may have been scaled down from a bulk recipe. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.