Preheat oven to 350ºF (180°C).
Grease with 1 tablespoon soft shortening a large 10 or 12-cup bundt cake pan. I use my fingers, but you can use a brush. Make sure every nook, cranny and angle is covered. Flour it, shaking off excess. Reserve.
Beat 3 eggs, ¾ cup vegetable oil and 1 ½ cups white sugar in a large bowl until foamy and thick, about 1 minute.
Add the sifted dry ingredients: 2 cups all-purpose flour, 1 ½ teaspoons baking powder, ½ teaspoon baking soda, ½ teaspoons salt and ½ teaspoon ground cinnamon. Mix well, but don't overmix.
Add 1 teaspoon vanilla extract and 2 cups unpeeled, grated zucchini. Mix well with a spatula making sure the zucchini is integrated.
Pour the zucchini batter into the prepared bundt pan.
Sprinkle streusel over the batter and bake for 40 to 45 minutes, until a tester inserted comes out clean.
Let cool on wire rack for 15 minutes and carefully check that it's not sticking to the edges. Shake it lightly and see if the cake loosens up. You can use a small smooth bladed knife to separate the edges. Shake the pan again and make sure the bottom is loose.
Invert onto a wire rack and let cool completely before glazing.
Keep leftovers covered for a day or two at room temperature and then refrigerate or freeze, always well wrapped.