Step 1 Cook risoni in a large saucepan according to packet instructions until tender; drain and refresh in cold water. Drain pasta again and transfer to a large salad bowl.
Step 2 Meanwhile, slice each chicken breast horizontally through centre to make 2 thin fillets and place in a large bowl. Add garlic, oregano lemon zest, 1 tablespoon of the lemon juice and half the olive oil to bowl; toss to coat.
Step 3 Spray a large chargrill pan with olive oil; set over high heat. Add zucchini; cook for 1–2 minutes per side, or until tender and charred. Transfer zucchini to pasta bowl.
Step 4 Cook chicken in same pan for 2 minutes per side, or until browned and cooked through. Add spinach and tomatoes to pasta salad bowl with remaining lemon juice and olive oil; toss.
Step 5 Cut chicken into slices. Divide risoni salad among 4 plates, top with chicken and serve.