Soak rinsed mung beans in a large bowl of water overnight. If short on time, boil a pot of water, turn off the heat, add mung beans, and let them soak for 1-2 hours.
Preheat oven to 350°F/180°C. Line a 12×8-inch baking dish or 8-inch square pan with parchment paper.
Add zucchini, cheese, and onions to a large mixing bowl.
Drain soaked mung beans and add to a blender.
Add remaining ingredients to the blender and blend on high until smooth.
Pour the mung bean mixture into the mixing bowl with the veggies and cheese. Mix until everything is well combined.
Transfer the mixture into the lined baking dish.
Bake for 35-40 minutes, until the filling is set and the edges are golden.
Cool for at least 10 minutes before slicing. To store, cool completely, then cover and store in the fridge for up to 5 days.