Drain the lentils. Pour rice into a fine mesh strainer and rinse under running water until the water runs clear.
Add the lentil-rice mixture and 8 cups water to a deep cooking pot and cook on medium heat, partially covered, for 15 minutes.
Add the turmeric, half the diced carrots and zucchini, and stir. Cook another 20–25 minutes, covered, or until the vegetables, rice, and lentils are mushy and soupy.
Meanwhile, heat avocado oil in a medium saucepan over medium heat until shimmering, about 3 minutes. Add half the mustard seeds, half the cumin seeds, half the curry leaves, and the remaining carrots and zucchini. Cook, stirring occassionally, until tender, 7 to 10 minutes. Set aside.
In a smaller pan, heat the vegan butter over medium heat. Add the remaining cumin and mustard seeds and fennel seeds. Cook for a few minutes to release aromatics, and until the mustard seeds have popped. Add the curry leaves and ginger, and stir to combine.
Remove from heat and add to the rice-lentil mixture along with the coconut milk (if using), coriander, salt, and garam masala. Stir to combine.
Feel free to add more water if you prefer a soupier texture. I adapt it depending on how my body’s feeling.
Top with cooked carrots and zucchini. Serve with green chutney, vegan yogurt, or simply enjoy it by itself.