Having homemade pesto in the freezer helped to streamline this dish. Here is the way our dinner came together.

While the water was coming to a boil John zoodled the zucchini and I sautéed onions and garlic. As the pasta was cooking, I put the frozen pesto in with onions and garlic. It was defrosted by the time the spaghetti was cooked. Then John drained the al dente spaghetti, reserving a cup of the pasta water. He added the pasta to the pesto mixture. I cooked the pasta and pesto together adding some of the pasta water to get a good consistency. Then I shut off the heat and added the zucchini noodles and mixed them in with spaghetti. If you try cooking them they disintegrate. The zoodles are warmed through just with the heat from the other cooked elements.