Preheat the pan: Set a large skillet or grill pan over medium-high heat.
Let it get hot for 2–3 minutes. A hot pan gives you the best sear.
Prep the veggies: Pat zucchini and squash dry with paper towels. Toss with 1 tablespoon olive oil, half the salt, and half the pepper.
Sear in batches: Add a thin film of oil to the hot pan.
Spread a single layer of squash and zucchini—don’t crowd. Cook 3–4 minutes without moving until the underside is nicely browned.
Flip and finish: Flip and cook another 2–3 minutes until tender with a little bite. Transfer to a bowl and repeat with the remaining slices, adding more oil as needed.
Add seasoning: Return all the cooked veggies to the pan over medium heat.
Add remaining salt and pepper, Italian seasoning, and garlic. Cook 30–60 seconds, just until fragrant.
Brighten it up: Turn off the heat. Stir in lemon juice, lemon zest, red pepper flakes (if using), and fresh herbs.
Serve: Taste and adjust seasoning.
Finish with a drizzle of olive oil and a sprinkle of Parmesan or feta if you like.