Preheat oven to 400 degrees F. From lemon, grate 1 teaspoon peel and squeeze 2 tablespoons juice.

In medium bowl, combine lemon juice, yellow squash, shallot, oregano, oil, 1/2 teaspoon salt, and 1/4 teaspoon coarsely ground black pepper.

Place parchment rectangles on work surface with a short side of parchment closest to you. On half of each parchment rectangle, arrange one-sixth of zucchini slices lengthwise, overlapping slightly, 2 inches from edge closest to you. Place salmon on zucchini; sprinkle with lemon peel and 1/2 teaspoon salt, then top with yellow-squash mixture. Fold other half of parchment over ingredients. To seal packets, begin at 1 corner and tightly fold edges of paper over about 1/2 inch all around, overlapping the folds.

Place packets on large cookie sheet. Bake 17 minutes or until salmon turns opaque throughout (to check for doneness, open 1 packet first, being careful to avoid escaping steam). To serve, carefully cut all packets open, and with spatula, gently transfer salmon and vegetables to 6 dinner plates. Spoon any liquid remaining in parchment over salmon and vegetables.