Heat olive oil in a large pot over medium heat.
Sauté the diced onion, carrots, and celery until softened, about 5 minutes.
Add the minced garlic and sauté for an additional 30 seconds until fragrant.
Stir in the zucchini, red bell pepper, and dried herbs, cooking for about 3 minutes.
Add the canned tomatoes and vegetable broth, stirring to combine.
Bring the soup to a boil, then reduce heat and let it simmer for 20 minutes.
Add the spinach and lemon juice, stirring until the spinach wilts.
Taste the soup again, adjusting seasoning if necessary, then serve hot.