In a medium bowl, whisk together the flour, salt, baking powder, baking soda, and spices. In a separate large bowl, combine the oil, sugars, vanilla and eggs until blended. Gradually add the flour mixture until just barely combined - you should definitely still see patches of flour streaked throughout. Gently fold in the zucchini and walnuts and just barely mix in. You do NOT want to over-mix the batter as this will lead to tough bread or bread that's sunken in the middle after baking.