Preheat oven to 350°F/180°C. Line or lightly grease an 8x8-inch baking dish (or similar size).
In a large mixing bowl, whisk soy milk and peanut butter until well combined.
Mix in shredded zucchini, mashed banana, vanilla extract, and sweetener if using.
Add oats, baking powder, cinnamon, chocolate chips, and salt. Mix until well combined.
Transfer the oat mixture to your prepared baking dish. Bake for 40-60 minutes until the center is set. Bake time will vary depending on your oven and how much moisture is in the zucchini.
Remove from oven and cool at least 5 minutes before serving. The oats will firm up more as it cools.