4 tablespoons olive oil, divided
1 1/2 cups coarse fresh breadcrumbs (from about 4 ounces crusty bread)
1 1/4 teaspoons kosher salt, divided, plus more as needed
Freshly ground black pepper
Finely grated zest of 2 medium lemons, divided
1 pound dry spaghetti
3 cups cooked or roasted Brussels sprouts, coarsely chopped if large
1 clove garlic, minced
1/4 teaspoon red pepper flakes (optional)
1/2 cup dry white wine
2 tablespoons freshly squeezed lemon juice, plus more as needed
Grated Parmesan cheese, for serving