Place an oven rack in the center of the oven and preheat to 350 degrees F.
In a small bowl, whisk together the oil, chili powder and lime zest if using. Brush the mixture on both sides of the bread halves using a pastry brush. Sprinkle the breads with the salt and pepper. Cut each bread half into 8 wedges and place in a single layer on a baking sheet. Bake until crisp and golden, 15 to 18 minutes.
Combine the beans, avocado, arugula, parsley, lemon juice, garlic, salt and pepper in the bowl of a food processor. Pulse until the mixture is coarsely chopped. Gradually add the olive oil until the mixture is creamy. Season with salt and pepper.
Spoon the hummus into a serving bowl and serve the pita chips alongside.