4 tablespoons olive oil, divided
3/4 cup panko breadcrumbs
1/2 cup grated Parmesan cheese
2 medium shallots, thinly sliced
2 cloves garlic, minced
2 pounds summer squash, cut crosswise into 1/4-inch pieces
1 tablespoon fresh thyme leaves
Finely grated zest from 1/2 lemon
1/2 teaspoon kosher salt
Freshly ground black pepper
Arrange a rack in the middle of the oven and heat to to 400°F. Place 2 tablespoons of the oil, panko, and Parmesan in a medium bowl and mix to combine; set aside.
Heat the remaining 2 tablespoons oil in a 6- to 8-inch oven-safe frying pan or skillet over medium heat until shimmering. Add the shallots and cook, stirring occasionally, until soft and fragrant, 3 to 4 minutes. Add the garlic and cook for 1 minute more.
Remove the pan from the heat and add the squash, thyme, lemon zest, and salt. Season with pepper, stir to combine, and spread into an even layer. Sprinkle the panko mixture evenly over the squash.
Transfer the skillet to the oven and bake until the top is golden-brown, 25 to 30 minutes. Let cool for about 5 minutes before serving.