To make tahini sauce, food process tahini, yogurt, garlic and 1 tablespoon lemon juice until smooth and creamy.
To make vinaigrette, combine remaining lemon juice, vinegar, zest, sugar, Dijon and olive oil in a mason jar and shake well to combine. Season with salt and pepper.
Chop all the vegetables and combine with herbs and onion. Add shredded lettuce. Toss with vinaigrette and half the pita chips.
Smear 1/3 of the tahini sauce on a serving platter or individual plates and top with salad; sprinkle with sumac.
Toss remaining tahini sauce and pita chips with chick peas and chicken; sprinkle with pine nuts and pomegranate seeds and serve next to fatoush.