Preheat the oven to 350°F and grease the bottom and sides of a 9 x 13 inch baking pan.
Stir ½ cup of the milk together with the ground flaxseeds in a large mixing bowl. Set this aside, making sure to let it sit for at least five minutes to gel.
In a separate mixing bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, cloves, and salt. Set this aside.
Stir the vegetable oil, vanilla, apple cider vinegar, and the remaining ¼ cup of milk together in a small container such as a liquid measuring cup. Set this aside.
Add the brown sugar and granulated sugar to the bowl with the flax mixture. Use an electric mixer to beat the ingredients together for about 30 seconds, until completely blended and slightly frothy.
Beat about a third of the flour mixture into the flax mixture, using the mixer at low speed. Next, beat in about a third of the oil mixture. Alternate adding the flour mixture and oil mixture until the batter is completely combined.
Fold in the shredded zucchini, walnuts, and raisins.
Pour the batter into the prepared baking pan.
Bake the cake for about 40 to 45 minutes, until a toothpick inserted into the center comes out clean.
Place the pan on a cooling rack and let the cake cool completely.
Once the cake is cool, you can optionally top it with powdered sugar or frosting (Note 1). Slice and serve.