Preheat the oven to 375°F. Boil the shells according to the package instructions. Reserve 1/2 cup of paste water before draining it. Stop cooking them as soon as they are al dente by draining them and spreading them out onto a baking sheet.
Prepare the other ingredients while the pasta is cooking. Shred the zucchini, then press on the shreds with a napkin or towel to absorb the extra liquid.
Heat a large saucepan over medium-high heat, then add the olive oil. Sauté the onions for 3 minutes until they're translucent. Add the garlic, zucchini, and baby spinach. Continue to stir as they cook for 5 minutes or until softened.
Combine the sautéed vegetables with the vegan cream cheese, hummus, 1/2 cup vegan mozzarella, basil leaves, salt, pepper, and oregano.
Pour the jar of pasta sauce into a 9x13 oven-safe dish. Add 1/2 cup of pasta water to the sauce jar. Close it and shake it. Add this mixture to the baking dish.
Put the creamy shell filling into a piping bag and stuff each shell with 1-2 tablespoons. You can alternatively use a spoon for this. Nest the shells into the sauce. This should make about 25 shells.
Sprinkle the remaining vegan mozzarella shreds over the shells. Cover the dish with a lid or foil and bake it for 25 minutes. It is ready when the sauce is bubbling, and the cheese is mostly melted. Garnish with fresh basil and enjoy!