Bring a saucepan of water to a boil. Stir in rice; reduce to a simmer. Cook until rice is tender, about 20 minutes. Drain, rinse with warm water, and set aside, covered.
Heat oil in a high-sided skillet on medium-high heat. Add pork; saute stirring occasionally, until brown on all sides, 3 to 4 minutes. Transfer pork to a plate; cover.
Place 1/2 cup stock, garlic, onion, celery, and carrots in pan. Cook, stirring occasionally until they soften, about 3 minutes. Add zucchini, squash, and peppers. Toss well; cook until soft, about 5 minutes.
Stir in remaining 1/2 cup stock and tomatoes with juice, breaking tomatoes apart with a spoon. Stir in thyme and parsley.
Return pork to pan, reduce heat to low, cover, and simmer until pork and vegetables are tender, about 20 minutes. Season with salt and pepper; serve over reserved rice.