Lemony Chicken Kabobs

2 T. grated lemon peel
2/3 cup lemon juice
1/2 cup olive oil
2 garlic cloves, minced
2 T. sugar
2 T. vinegar
4 t. salt
1/4 t. ground red pepper
8 skinless, boneless chicken breasts, cubed
1 1/2 lb. small zucchini, sliced
1 lb. medium mushrooms, stems trimmed

Combine first 8 ingredients for the marinade. Pour over chicken and zucchini in a large bowl. Marinade in refrigerator 6-12 hours. Stir occasionally. Add mushrooms 1 hour before cooking. Drain chicken and zucchini and alternate on skewers, chicken, zucchini, mushrooms. Grill over medium heat till chicken tender (about 15 minutes) Brush kebobs with marinade.