Preheat the oven to 425 degrees. Heat the oil in a large saute pan over high heat. Add the zucchini, bell peppers, garlic paste and 1/4 teaspoon red pepper flakes. Season with salt and pepper and cook until the vegetables are almost soft, about 5 minutes. Set aside to cool.
Whisk the egg and fresh herbs in a large bowl. Add the turkey, panko, grated cheese, 1/2 cup ketchup, 2 tablespoons balsamic vinegar and the cooled vegetables; mix until just combined.
Gently press the mixture into a 9-by-5-inch loaf pan. Whisk the remaining 1/4 cup ketchup, 1/4 cup balsamic vinegar and 1/4 teaspoon red pepper flakes in a small bowl; brush the mixture over the entire loaf. Bake for 1 to 1 1/4 hours. Let rest for 10 minutes before slicing.