Preheat your oven to 350°F (175°C) and grease a 9x5 inch loaf pan with butter or cooking spray, then dust lightly with flour.

In a large mixing bowl, combine the dry ingredients: 2 cups of all-purpose flour, 1 teaspoon of ground cinnamon, 1 teaspoon of baking soda, ½ teaspoon of salt, and ½ teaspoon of ground nutmeg. Whisk until blended.

In a separate bowl, whisk together 1 cup of granulated sugar, ½ cup of vegetable oil, 2 large eggs, and 2 teaspoons of vanilla extract until smooth.

Carefully fold the wet ingredients into the dry mixture using a spatula until just combined, leaving some flour pockets.

Gently fold in 1 to 1.5 cups of grated zucchini and ½ cup of chopped walnuts or pecans if desired.

In a small bowl, combine the streusel topping ingredients: ½ cup of all-purpose flour, ¼ cup of light brown sugar, ¼ cup of granulated sugar, 1 teaspoon of ground cinnamon, and ¼ cup of cold unsalted butter. Mix until it resembles coarse crumbs.

Pour the batter into the prepared loaf pan, sprinkle streusel topping evenly, and bake for 50 to 60 minutes until golden brown and a toothpick comes out clean.

Remove from oven, let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.