Bring a large pot of well-salted water to a boil. It should taste like mild seawater. Add the spaghetti and cook according to package directions until just al dente, usually 8 to 9 minutes. Before you drain it, scoop out about 1/2 cup of pasta water and set it aside, then drain the pasta and set it aside.

While the pasta cooks, set a large skillet over medium heat. Add the diced pancetta and let it cook, stirring occasionally, for about 5 to 6 minutes until the fat has rendered and the pieces are golden and crispy. Use a slotted spoon to transfer the pancetta to a paper-towel-lined plate. Leave the rendered fat in the skillet.

In a separate small skillet over medium heat, melt the butter. Add the panko breadcrumbs and a pinch of salt. Stir constantly for 2 to 3 minutes until the crumbs are deep golden and smell nutty. Watch them closely because they can burn fast once they start to color. Immediately pour them onto a plate and spread them out so they stop cooking. Set aside.

Return the large skillet with the pancetta fat to medium-high heat. Add the zucchini slices in a single layer if possible and let them cook without stirring for 2 minutes so they pick up some color on one side. Stir, add the garlic and red pepper flakes, and cook another 2 to 3 minutes until the zucchini is tender but still has a little bite and the garlic is fragrant. Season with salt and pepper.

Pour in the white wine or chicken broth and let it bubble for about 1 minute, scraping up any browned bits from the bottom of the pan. Add the drained spaghetti directly to the skillet along with 1/3 cup of the reserved pasta water and the olive oil. Toss everything together over medium heat for about 1 minute until the pasta is coated and the sauce looks glossy. Add a splash more pasta water if it looks dry.

Remove the pan from the heat and stir in the Parmesan cheese and the crispy pancetta. Give it a taste and adjust salt and pepper as needed. Divide into bowls and top each serving generously with the toasted breadcrumbs. Serve immediately with extra Parmesan on the side.