Heat oil in a large pot over medium heat. Add onion; cook, stirring, until starting to soften, about 2 minutes. Add garlic; cook, stirring, until fragrant, about 30 seconds. Add green beans, zucchini and corn; cook, stirring, for 2 minutes. Add broth, kale, tomatoes, salt and pepper; increase heat to high and bring to a boil. Reduce heat to maintain a simmer; cook until the vegetables are soft, 12 to 15 minutes. Remove from heat and stir in lemon juice and herbs.