In a small bowl, mix chia seeds and water. Set aside for about 5 minutes. They will create a jelly-like substance that will act as the binding agent of the recipe in place of an egg.
In another small bowl, whisk together almond milk and lemon juice. Set aside for about 10 minutes. This will thicken and act as buttermilk.
In a large bowl, sift together flour, sugars, baking soda, baking powder, cinnamon and salt.
Mix in the oil, chia seed mixture and the almond milk mixture, just until combined. Do not overmix.
Fold in the zucchini, carrots, and walnuts gently, until evenly distributed in the batter. Batter will be pretty wet.
Spoon mixture into a greased muffin tin or ramekins, and bake at 350 for about 50 mins, until brown on top, and a butter knife comes out clean.