Greek Turkey Burgers with Tzatziki

Ingredients

• 4 teaspoons oil, divided
• 8 ounces mushrooms, diced small
• 1/2 red onion, diced small
• 2 cloves garlic, minced
• 1 pound ground turkey
• 1 small zucchini (about 4 ounces), unpeeled, diced small
• 1/2 teaspoon oregano
• 1 Tablespoon Worcestershire sauce
• 1 teaspoon Dijon mustard
• 3 whole wheat pita pockets, cut into quarters
• 1 cucumber, peeled, seeds removed, and diced small or grated
• 8 ounces non-fat or low-fat plain Greek yogurt
• Juice of half a lemon, or more, to taste
• 3 teaspoons dried dill or ⅛ cup fresh dill, chopped
• Salt and black pepper