Place a 22.5cm x 16cm (10 inch x 6 inch) baking dish into the oven and pre-heat to 350 F (180 C).
While the baking dish and oven are heating up, grate your potatoes (skins on), carrots (peel first), zucchini, and onion. Combine the scraps in a large bowl.
Move your scraps to a cheese cloth or colander to squeeze out the liquid over the sink. (I find a cheese cloth is easier to get more liquid out.) When done, let it rest on the counter.
Whisk four eggs with your spices, oil (or schmaltz), salt, and pepper until fluffy.
Put your scraps into a large bowl and pour the egg mixture over it. Add 25 grams or about three tablespoons of matzo meal and combine with your hands.
Take the pre-heated baking dish out of the oven and drop some butter or vegetable oil onto the dish to grease it. It should instantly sizzle. Once the pan is sufficiently greased, carefully transfer your kugel mixture into the baking dish. Don't be afraid to really pack it in.
When done, brush your remaining butter or a little bit of vegetable oil over the top and place it in the oven for 45 - 60 minutes. Check every now and again to make sure the top isn't browning too quickly. If so, cover with aluminum foil. The kugel is done when it has a nice golden top and you can stick something into the center and it comes out clean. If you have an instant-read thermometer, the center should read at about 160 F (71 C).
Let the kugel rest for about 5 to 10 minutes before cutting it up and serving.