Heat olive oil in a large pot over medium heat.
Add chopped onion and garlic; sauté until translucent.
Add bell pepper, carrots, and zucchini; cook for about 5 minutes.
Stir in the black beans, kidney beans, diced tomatoes, vegetable broth, chili powder, cumin, salt, and pepper.
Bring to a boil, then reduce heat and simmer for 20-30 minutes.
Serve hot, garnished with fresh cilantro or avocado if desired.
