How to Make It
Heat 1 tablespoon of the oil in a medium nonstick skillet over medium-high heat. Add the zucchini, squash, bell pepper, onion, ½ teaspoon salt, and ¼ teaspoon pepper and cook, tossing occasionally, until just tender, 2 to 3 minutes. Transfer to a plate and refrigerate until cool. Wipe out the skillet.
In a medium bowl, toss the cooled vegetables with the vinegar, parsley, basil, and 2 tablespoons of the oil.
Heat the remaining tablespoon of oil in the skillet over medium-high heat. Season the fish with ½ teaspoon salt and ¼ teaspoon pepper and cook until opaque throughout, 2 to 3 minutes per side. Serve with the salsa.