Pat the flank steak completely dry with paper towels. Season generously with salt, pepper, and garlic powder on both sides. In a bowl, mix olive oil, minced garlic, fresh parsley, cilantro, and lemon juice. Place steak in the marinade and coat thoroughly on both sides. Let sit for at least 15 minutes at room temperature, or up to 2 hours refrigerated.

Slice zucchini lengthwise into ¼ inch thick planks, not rounds. This prevents them from falling through grill grates. Brush both sides with olive oil and season with salt, pepper, and Italian seasoning. Set aside with the marinated steak.

In a small bowl, combine Greek yogurt with minced garlic. Add chopped parsley and cilantro. Squeeze in lemon juice and add a pinch of salt. Stir in olive oil for richness. Mix until smooth and creamy. Set sauce aside or refrigerate until ready to serve.

Heat your outdoor grill or grill pan to medium-high heat, about 400-450°F. Oil the grill grates well using a paper towel dipped in oil to prevent sticking. Make sure the grill is fully hot before adding food.

Place marinated steak on the hot grill. Cook for 4-5 minutes on the first side without moving it. Flip once and cook another 4-5 minutes for medium-rare. Add zucchini planks to the grill alongside the steak. Grill zucchini for 3-4 minutes per side until char marks appear and it's tender but not mushy.

Use a meat thermometer to check steak internal temperature. Remove when it reaches 130-135°F for medium-rare, or 140-145°F for medium. Remove zucchini when charred with grill marks. Transfer steak to a cutting board.

Let the steak rest undisturbed for 5 minutes before slicing. This allows juices to redistribute throughout the meat, keeping it tender and juicy. Do not skip this step or the juices will run out when you slice.

After resting, slice the steak thinly against the grain using a sharp knife. Cutting against the grain shortens the muscle fibers, making each bite tender. Aim for ¼ inch thick slices.

Place warm cooked rice or quinoa in the bottom of each serving bowl. Arrange sliced steak over the rice base. Add grilled zucchini planks next to the steak. Drizzle creamy garlic herb sauce generously over everything.

Top with fresh herbs like parsley or cilantro. Add optional toppings such as cherry tomatoes, feta cheese, red onion slices, or avocado. Squeeze fresh lemon juice over the entire bowl. Serve immediately while warm.