In a medium sized bowl combine the lemon juice, olive oil, balsamic vinegar, smoked paprika, oregano, garlic, salt and pepper. Add the zucchini + mushrooms and toss well, making sure the veggies are completely coated in the seasonings. Let sit for 10-15 minutes.
Meanwhile, preheat the oven to 425 degrees F.
Place the potatoes on a large baking sheet and drizzle with olive oil, salt + pepper. Gently toss with your hands or two spatulas to evenly coat. Bake for 15-20 minutes, then flip and bake for 15-20 minutes more. During the last 5 minutes of cooking, add the herbs and toss well. You want the potatoes to be tender, but crisp on the outside.
Heat your grill, grill pan or skillet to medium high heat.
Transfer the veggies, in batches if needed, to the grill and grill 3-4 minutes per side or until char marks appear. Remove everything from the grill. Alternately you can also roast the veggies at 425 degrees for 25-30 minutes or until soft.
To assemble, divide the grilled veggies among warm naan or pita, top with tomatoes, cucumber, olives and avocado. Add the fries and finish with a good sprinkle of feta cheese. Serve with the tzatziki (below)