1. Cut a small X in the bottom of each tomato. Bring a large pot of water to a boil. Place a large bowl of cold water with ice cubes next to it. Boil tomatoes for 1 minute, then immediately transfer to ice water with a slotted spoon to cool. Once tomatoes cool, remove peel and discard. Cut each in half and squeeze out seeds. Core tomatoes, and cut in 1-inch pieces.
2. Lightly coat grill rack or grill pan with nonstick cooking spray. Heat grill or grill pan to medium high. Season chicken on both sides with 1/4 teaspoon of the salt and 1/4 teaspoon of the pepper. Grill chicken, about 5 minutes per side until cooked through. Set aside to cool slightly, then cut into thin strips.
3. Cook pasta following package directions. Drain and toss in a large bowl with 2 tablespoons of the oil. Heat remaining 2 tablespoons oil in a 12-inch skillet over medium-high heat. Add garlic; cook 2 minutes. Add tomatoes, zucchini and yellow pepper; cook 3 more minutes. Add wine or pasta water, tomato paste, remaining 1-1/4 teaspoons salt and 1/4 teaspoon pepper; cook 3 minutes. Stir in chicken to heat through. Remove from heat. Toss sauce with pasta, basil and fresh mozzarella.