ORZO WITH SUMMER SQUASH AND TOASTED HAZELNUTS

1 1/2 cups orzo (10 oz)
3 tablespoons unsalted butter
3 tablespoons olive oil
1 cup finely chopped shallot (6 1/2 oz) 
2 medium zucchini (1 1/2 lb total), cut into 1/3-inch dice
2 medium yellow squash (1 lb total), cut into 1/3-inch dice
1 teaspoon salt
1/2 teaspoon black pepper
3/4 cup hazelnuts (4 oz), toasted, loose skins rubbed off in a kitchen towel, and nuts coarsely chopped 
1/2 cup chopped fresh flat-leaf parsley
1/2 cup chopped fresh basil
2 teaspoons finely grated fresh lemon zest

Cook orzo in a 4- to 5-quart pot of boiling salted water until al dente. Reserve 1/2 cup cooking water, then drain orzo in a colander. While orzo is cooking, heat butter and oil in a deep 12-inch heavy skillet over moderately high heat until foam subsides, then sauté shallot, stirring, until golden, about 5 minutes. Add zucchini, yellow squash, salt, and pepper and sauté, stirring occasionally, until vegetables are just tender, about 5 minutes. Remove from heat and stir in nuts, parsley, basil, and zest. Add cooked orzo to skillet and stir gently. If mixture seems dry, moisten with some reserved pasta water. Season with salt and pepper. Serve warm or at room temperature.