Preheat the oven to 400 degrees Fahrenheit.
Place chicken in Instant Pot with 1 c. water. Press the "Meat" button, and wait until the cycle completes. Release the pressure manually. Carefully remove the lid and shred the chicken reserving the cooking liquid. Alternatively, poach the diced chicken in a saute pan with a lid for about 15 minutes.
Heat the olive oil in a large pan over medium heat and add the diced onion and zucchini, sweating until tender. Add the garlic and stir well, cooking until fragrant.
Add the spices and sea salt. Add the reserved cooking liquid and stir well to combine and bring to a simmer for a few minutes to heat through.
Spoon half of the vegetable mixture into an oven-proof casserole dish. Shred half the chicken over the top of the vegetable layer. Top the chicken with half of the grated cheese.
Repeat the process with another layer of vegetable mixture, the remaining chicken (shredded) and a final layer of cheese.
Transfer the pan to the oven to bake for 18-20 minutes until the sauce is bubbling, the chicken is cooked through and the cheese is melted and golden.
Serve immediately or portion into glass containers for freezing.