4 teaspoons extra-virgin olive oil, divided
2 large red bell peppers, diced
2 pounds asparagus, trimmed and cut into 1-inch lengths
2 teaspoons freshly grated lemon zest
1/2 teaspoon salt, divided
5 cloves garlic, minced
1 pound raw shrimp, (26-30 per pound), peeled and deveined
1 cup reduced-sodium chicken broth
1 teaspoon cornstarch
2 tablespoons lemon juice
2 tablespoons chopped fresh parsley