Heat olive oil in a large pot or large Dutch oven over medium-high heat. Add diced onion, carrots, celery, zucchini, and peppers. Stir with a wooden spoon, cooking for 5 minutes.
Stir in salt, black pepper, and spices (garlic, chili powder, lemon zest, cumin, rosemary, paprika, basil, onion powder, garlic powder, and bay leaf). Cook for 2–3 minutes until fragrant.
Add tomato paste, lemon juice, soy sauce, 6 cups of vegetable stock, corn, garbanzo beans, diced tomatoes, and brown rice. Stir well and bring to a boil.
Cover, reduce the heat to low, and let the soup simmer for 30–45 minutes until the brown rice and vegetables are tender.
Stir in fresh baby spinach and frozen peas. Cook just until warmed through. Taste and adjust seasoning if needed. Thin the soup with the reserved vegetable stock to the desired consistency.