Preheat the oven to 325 degrees F (165 degrees C). Grease and flour two 8x4-inch pans.
Sift flour, salt, baking powder, baking soda, and cinnamon together in a large bowl.
Beat eggs, oil, sugar, and vanilla together in a separate large bowl with an electric mixer until combined; add flour mixture and beat well. Stir in zucchini and walnuts until well combined. Pour batter into the prepared pans.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 40 to 60 minutes. Cool in the pans on a wire rack for 20 minutes. Run a table knife around the edges to loosen. Invert carefully onto a wire rack and let cool completely.