In large bowl, combine garlic, lemon zest, juice, cilantro, and yogurt. Pack half the yogurt mixture in a sealable container to be used as a dip and refrigerate. Set aside remainder to use as marinade while you prepare the chicken.
On cutting board, lay sheet of parchment paper, then chicken pieces, and then cover with a second sheet of parchment paper. Using a large rolling pin or meat tenderizer, pound meat to flatten. This will ensure pieces cook evenly.
Brush marinade onto each side of each piece of chicken and layer chicken in sealable storage container suitable for transporting in your cooler. Add in any remaining marinade. Seal container and refrigerate, or place in your cooler until ready to grill. Allow chicken to marinate for at least 4 hours and no more than 24. When ready to eat, grill each chicken piece on hot grill for 3 to 5 minutes per side, or until meat releases easily from grill. Discard any excess marinade. Serve with reserved yogurt dip.
Per serving: 361 calories; 50 g protein; 17 g total fat (2 g sat. fat); 8 g total carbohydrates (5 g sugars, 1 g fiber); 190 mg sodium