Prepare orzo per package directions. Drain well, then transfer to large bowl; toss with 1 tablespoon oil.

Meanwhile, heat remaining tablespoon oil in large skillet on medium. Season chicken with ½ teaspoon each salt and pepper and cook until golden brown and cooked through, 5 to 7 minutes per side; transfer to plates.

In another large bowl, whisk together vinegar and 1/4 teaspoon each salt and pepper. Add zucchini and squash and toss to combine. Let sit until orzo is done, at least 5 minutes.

With slotted spoon, transfer vegetables to bowl with orzo, leaving vinegar in bowl, and toss to combine.

Whisk pesto into vinegar, then drizzle over orzo and sprinkle with almonds. Serve with chicken.