Heat olive oil in large nonstick skillet over medium heat. Saute onions for 2 minutes. Stir in zucchini, carrot and bell pepper and saute another 5-7 minutes. Stir in garlic until fragrant, another minute or so.
Mix tomato paste into sauteed vegetables and then pour in remaining ingredients for the sauce. Bring to boil and then reduce to simmer.
Cover and cook for 30 minutes or longer if need be. The sauce will thicken, so thin out with a little water if you like it runny.