Preheat your oven to 350°F (175°C). This ensures your cake bakes evenly.
Grease your 9x13 inch baking dish with a bit of olive oil or butter to prevent sticking. You can also line it with parchment paper for easier removal.
In a large mixing bowl, whisk together the all-purpose flour, salt, baking soda, baking powder, and cinnamon.
In another bowl, beat the eggs. Add the olive oil, sugar, and vanilla extract. Mix until well combined.
Grate your zucchini and fold it into the wet mixture. Make sure to squeeze out excess moisture if it’s particularly watery.
Slowly add the wet ingredients to the dry ingredients, stirring gently until just combined. Be careful not to over-mix; a few lumps are okay.
In a separate bowl, combine the brown sugar, flour, and cinnamon for the streusel. Cut in the unsalted butter until the mixture resembles coarse crumbs.
Pour half of the batter into the prepared baking dish. Sprinkle half of the streusel mixture over the batter. Add the remaining batter on top and finish with the rest of the streusel.
Place the baking dish in the preheated oven and bake for 40-45 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes. Then transfer it to a cooling rack to cool completely before slicing.
