Heat 1 tablespoon of olive oil in a large stockpot or dutch oven over medium-high heat. Once hot, season both sides of the chicken breasts with salt and freshly cracked black pepper, and add the chicken to the pot. Sear for 3 minutes, flip, and sear for another 3 minutes. Transfer the chicken to a plate for now.
Add the remaining 1 tablespoon of olive oil to the pot. Add onions, celery, and carrots. Saute for 3 to 5 minutes.
Add the garlic powder, Italian seasoning, crushed red pepper flakes, and tomato paste. Cook, stirring often, for 2 minutes.
Add the fire-roasted diced tomatoes, potatoes, and chicken broth to the pot and bring to a boil.
Add the chicken to the soup, reduce the heat to a simmer, and cover. Cook for 15 to 20 minutes, or until the internal temperature of the chicken reaches 165ºF. Remove the chicken to a cutting board.
Add the zucchini, green beans, and corn. Cook covered for 6-8 minutes over medium-low heat, until the zucchini is tender.
Meanwhile, shred the chicken. When the zucchini is tender, add the shredded chicken and lemon juice to the soup. Stir to combine. Serve.