Preheat the oven to 350 degrees F (175 degrees C). Generously butter two loaf pans.
Mix kosher salt into zucchini and let sit for 10 minutes. Transfer to a strainer and rinse very thoroughly under cold water to remove salt. Let drain for 15 to 20 minutes before using.
Whisk flour, baking powder, baking soda, cinnamon, ginger, cayenne, and nutmeg together in a mixing bowl. Reserve until needed.
Combine eggs, sugar, and vanilla in another large mixing bowl, and whisk until mixture is smooth and turns a pale yellow, about 1 minute. Grab a handful of the drained zucchini with both hands and squeeze out any excess water before transferring into the egg-sugar mixture. Repeat until all the zucchini has been transferred in.
Pour in melted butter and stir until combined. Stir walnuts into the batter, followed by the flour mixture. Use a spatula to mix until the flour disappears.
Transfer into the prepared loaf pans. Tap pans on the countertop to settle the batter.
Bake in the center of the preheated oven until golden brown on top and a skewer poked in the center comes out clean, about 50 minutes. Let cool for 10 minutes in the pan, and then turn out on to a cooling rack. Let cool completely before serving.