In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until translucent.
Stir in the minced garlic, diced carrots, and celery. Cook for another 5 minutes, stirring occasionally.
Add the zucchini and green beans to the pot, cooking for an additional 3 minutes.
Pour in the vegetable broth and bring the mixture to a boil. Reduce the heat and let it simmer for 10 minutes.
Add the peas, thyme, salt, and pepper. Continue to simmer for another 5 minutes.
Stir in the fresh spinach and lemon juice, cooking just until the spinach wilts, about 2 minutes.
Taste and adjust seasoning if necessary. Serve hot, garnished with fresh parsley.