Set oven to 350°F (175°C). Grease four medium loaf pans or line with parchment paper.
In a large bowl, beat together sugar, eggs, oil, and vanilla until smooth using an electric mixer.
Add flour, salt, baking soda, baking powder, nutmeg, and cinnamon. Mix on low speed until just combined.
Gently stir in shredded zucchini, blueberries, and walnuts (if using) with a spatula. Mix just until evenly distributed.
Divide batter evenly between pans. Bake for 1 hour, or until a toothpick comes out clean or with moist crumbs.
Cool loaves in pans for 10 minutes, then transfer to a wire rack. Once fully cooled, wrap well if freezing.