SKIP this step if you want it to be vegetarian, if not proceed: In a large skillet {with high sides}, cook ground beef over medium heat, breaking apart as you go. Once beef is cooked thoroughly, drain {and rinse under hot water--only if you're crazy about making low-fat meals...like me :)}
Wipe out the same pan with a paper towel and heat olive oil 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.