Pre-heat oven to 400 degrees and lightly spray a donut pan with cooking spray.
In a small bowl, mix together both flours, wheat germ, brown sugar, baking powder, cinnamon, salt, and baking soda.
In a large bowl, combine the grated carrots, zucchini, yogurt, egg yolks, syrup, and orange zest.
Slowly fold the flour mixture into the carrot mixture until just combined, taking care not to over-mix.
In a separate large bowl with a hand mixer (or in the bowl of a stand mixer with whisk attachment), beat egg whites until shiny, stiff peaks form. Gently fold stiff egg whites into the carrot mixture.
Spoon batter into prepared donut pan filling just about to the top. I like to put my batter in a little plastic bag with the corner cut off, so I can squeeze it into donut pan.
Bake for about 10 minutes, until donuts are turning golden and a toothpick inserted into the center of one of the donuts comes out clean.
Let donuts cool in the pan for a couple minutes before moving to wire racks to cool completely.
Once donuts are completely cooled, dip them in yogurt frosting. I like to double dip.