Bring a large stock pot of water to a boil. While you are waiting for the water to boil, place 4 tbsp olive oil in a sauté pan. Turn the heat onto medium and add the garlic and onions. Cook until the garlic and onions begin to soften, but not brown, about 3-5 minutes. Add the zucchini. Stir to coat and cook until the zucchini have just started to soften but still have a little bite to them, about 5 minutes. Season with sea salt and pepper. Taste.
Remove from the heat and add the toasted pine nuts. Set aside while the pasta cooks. Once boiling, season generously with sea salt and add the pasta. Cook until al dente.
Scoop the cooked pasta into the sauté pan with the zucchini mixture. Stir to coat. Add lemon zest and the juice of one lemon. Stir. Taste. Season with more sea salt, black pepper, and olive oil as necessary. Scoop the pasta into individual bowls and top with crumbled feta, black pepper, basil, and a little lemon zest. Finish with a teaspoon or two of the pasta water.