Threading the pork and vegetables on separate skewers ensures that everything--the juicy pork cubes, tender crisp zucchini, yellow squash, and just warmed cherry tomatoes--will be perfectly cooked.
In a small bowl, whisk oil, garlic and lemon zest and juice. Stir in parsley, rosemary, thyme, sugar, 1/2 teaspoon of the salt and all the pepper.
Place pork in a large resealable food-storage bag and spoon in 4 tablespoons of the herb-oil mixture. Place zucchini, squash and tomatoes in another large resealable bag; pour the rest of the herb-oil mixture into it. Seal both bags and shake to coat ingredients. Refrigerate for 1 hour, turning after 30 minutes.
Heat a gas grill to medium-high or prepare a charcoal grill with medium-hot coals.
Thread metal skewers separately with pork, zucchini, squash and tomatoes. Grill zucchini and squash about 5 minutes per side, pork about 3 minutes per side or until internal temperature reads 155 degree F on an instant-read thermometer. Grill tomatoes about 3 minutes per side.
To serve, sprinkle kabobs with remaining 1/4 teaspoon salt.