For the lemony oregano chicken skewers, first prepare the marinade. To do this, whisk together everything except the oil in a bowl. Then slowly add the olive oil and continue whisking until all the ingredients are combined.
For the skewers, soak 2 wooden skewers in water for at least 1 hour. Add the chicken to the marinade and let marinate for at least 2 hours in the refrigerator or 30 minutes at room temperature.
Heat a grill or grill pan over medium or high heat. Thread the chicken pieces onto the skewers, alternating with the onion, and pour away the marinade. Season each skewer with salt and pepper to taste. Grill for 8 to 10 minutes, turning occasionally, until all sides are browned and the pieces of meat are cooked.
For the salad, preheat the grill. In a bowl, mix everything except the tomato and marinate for a few minutes. Take out the zucchini and set the dressing aside. Grill the zucchini for about 2 minutes per side. Then dice the zucchini and mix with the diced tomatoes. Drizzle with the leftover dressing.
Serve the lemony oregano chicken skewers with summer grilled salad.