First make the zoodles. Wash the zucchini and cut off the ends. Then either use a spiralizer or a handheld spiralizer to cut them into long thin strips that resemble spaghetti.
Then make the marinade. Fill a medium bowl with water and bring it to a boil. Add the whole tomatoes and leave them in the boiling water for about 1 minute. Then drain and rinse with very cold water. The tomato skin should be wrinkled and coming off the flesh easily. Peel the tomatoes with your hands or use a small knife.
Finely dice the tomatoes. Chop the onion and the garlic.
Heat some oil in a large pot and sauté the onion for about 3 minutes or until translucent. Then add the garlic and cook for another minute. Stir in the tomato paste and the sugar and cook for 2 more minutes.
Now add the white wine vinegar and the diced tomatoes. Stir well and let it simmer for about 20 minutes. At the end of the cooking time, season it with salt, pepper, oregano, and basil.
While the tomato sauce is cooking, heat some olive oil in a large pan and cook the zoodles for about 3-5 minutes on low to medium heat. Put them on plates and add the homemade marinara sauce on top. If you want you could also add some vegan Parmesan or shredded cheese on top.
Notes
It's important not to add any salt to the zoodles themselves. Instead just season the marinara with salt and pepper. If you add salt to the zucchini, they most likely become mushy or when you add the sauce on top it becomes watery very quickly.
Don't heat the zoodles for more than 3-5 minutes because otherwise they will lose too much water and they will become watery.
If you don't have a spiraziler, you could also use a julienne peeler or a mandolin. However, it's way easier with a Spiralizer.