Heat olive oil in a large pot over medium heat.
Add diced onion, carrots, and celery. Sauté for about 5 minutes until softened.
Stir in garlic, thyme, salt, and pepper. Cook for another minute until fragrant.
Add diced potatoes, zucchini (if using), and the can of diced tomatoes (with juice).
Pour in the vegetable broth and bring everything to a gentle boil.
Reduce heat, cover, and let simmer for 20 minutes.
Add green beans and corn. Continue simmering uncovered for another 15–20 minutes, until all vegetables are tender.
Taste and adjust seasoning if needed.
Garnish with fresh chopped parsley and serve warm with bread or crackers.