In a medium bowl, combine the lemon juice, lemon zest, minced garlic, olive oil, soy sauce, smoked paprika, oregano, salt, and pepper. Whisk until well mixed.
Place the chicken thighs in a zip-lock bag or shallow dish and pour half of the marinade over them. Seal the bag/dish and marinate in the refrigerator for at least 30 minutes (or up to 2 hours for more flavor).
Preheat your grill or a grill pan over medium-high heat. Add a light coat of oil to prevent sticking.
While the grill is heating, toss the sliced zucchinis with the remaining marinade in a bowl, ensuring they are well coated.
Once the grill is hot, remove the chicken from the marinade and place it on the grill. Cook for 6-7 minutes per side or until the internal temperature reaches 165°F (75°C).
In the last few minutes of grilling, add the marinated zucchini slices to the grill. Cook for about 3-4 minutes, turning occasionally until they are tender with nice grill marks.
Remove the chicken and zucchini from the grill, and let the chicken rest for a few minutes.
Slice the chicken and serve it on a platter alongside the grilled zucchini. Garnish with fresh parsley for a pop of color.
Notes
Marinate the chicken for up to 2 hours for enhanced flavor.