Heat the oven to 425°F.

• Lightly grease a sheet pan [2 sheet pans] with 1 to 2 teaspoons oil. 
• Cut a small corner from the ground chicken packaging and drain off any excess liquid. Transfer to a plate; pat dry with a paper towel. 

In a medium bowl, lightly beat the egg with a fork until blended. Add the chicken, season generously with salt and pepper, and mix until just combined. Transfer the meat mixture to the prepared sheet pan [2 sheet pans] and, using your fingers, form into a 6-by-8-inch rectangle [2 rectangles] about ½ inch thick. Bake until the chicken is almost cooked through, 6 to 8 minutes.

While the crust bakes, prepare the toppings.

• Cut the zucchini in half lengthwise, then crosswise into thin half-moons.
• Thinly slice the mushrooms.
• Peel the onion, cut in half lengthwise, then thinly slice crosswise.
• Cut any large roasted garlic cloves in half lengthwise or into quarters, if desired.

Remove the sheet pan from the oven. Spread the marinara evenly over the crust, leaving a ½-inch border around the edges. Top with the zucchini, mushrooms, and as much onion, garlic, and olives as you like. Season with salt and pepper. 

Return to the oven and bake until the vegetables are lightly browned and tender and the chicken is cooked through, 6 to 8 minutes. Remove from the oven, add dollops of the arugula pesto, and season to taste with salt and pepper. Cut into fourths on the diagonal. 

Transfer the meatza to individual plates and serve.