Cut chicken breasts in half horizontally. Place the chicken pieces between plastic wrap. Use a meat mallet or rolling pin to gently pound to an even thickness.
Place the flour on a large plate. Season with pepper. Lightly beat the eggs in a shallow bowl. Mix lemon rind, thyme and breadcrumbs on a separate large plate or tray.
One piece at a time, dust chicken in the flour, dip into egg and then evenly coat with the breadcrumbs. Line a baking tray with baking paper. Spray paper lightly with cooking spray. Place chicken on prepared tray. Refrigerate for 10 minutes.
Lightly spray with cooking spray. Bake in a 220 °C oven (200 °C fan-forced) for 20-25 minutes or until lightly golden and cooked through. Turning schnitzels halfway through cooking time and spraying again with cooking spray.
Meanwhile boil, steam or microwave potatoes and zucchini separately until tender. Drain. Transfer to a large bowl. Add parsley. Toss gently. Season with pepper. Serve chicken with vegetables and lemon wedges.