Preheat oven to 350°F or 180° C.
Grate carrot and zucchini. Squeeze extra water from veggies and keep aside. It should be about 1 cup to ¾ Cup.
Sieve together whole wheat flour, baking soda, baking powder, cocoa powder, and salt.
Chop the nuts(pecans and walnuts) finely.
Prepare buttermilk. Add apple cider vinegar in milk and keep aside. Do not stir it.
Beat oil and sugar in a bowl, till sugar dissolves.
Add vanilla essence, sour cream and mix well.
Add grated carrots and zucchini.
Add sieved flour along with buttermilk and fold the batter. Don't overmix it. Also, don't add all the buttermilk, just the right amount to get a thick lumpy batter as carrots and zucchini will leave water will baking.
Fold in half of the chopped nuts.
Transfer the batter to a well greased and dusted loaf pan. Top with the remaining chopped nuts.I have used 9"X 5" loaf pan (about 3 " tall).
Bake for 50-60 minutes in a preheated oven at 350°F or 180°C.
After 45 minutes, check for the doneness by inserting a toothpick in the center of the bread. If it comes out clean bread is done. If there is batter sticking to it and top seems to be done, cover the pan with an aluminum foil and bake for another 10-15 minutes.
Once done, take out of the oven, leave on the counter for 5 minutes and then carefully transfer the bread on wire rack to cool.
Cut bread when it completely cools down.
Store in an airtight container.