Prepare yum yum sauce: In a medium bowl, whisk together mayonnaise, melted butter, tomato paste, sugar, garlic powder, paprika, and cayenne. Add water 1 tablespoon at a time until sauce reaches pourable consistency. Refrigerate while preparing meal.
Prepare hibachi sauce: In a medium bowl, whisk together soy sauce, honey, brown sugar, minced garlic, and minced ginger until smooth. Set aside.
Cut chicken breast into uniform 1-inch cubes. Pat dry with paper towels and set aside. Refrigerate until ready to cook.
Preheat your Blackstone griddle with two distinct heat zones: medium-high heat (400-450°F) for the chicken zone, and medium-low heat (300-325°F) for the rice zone. Verify temperature with infrared thermometer.
Start with fried rice: Add butter and sesame oil to the medium-low zone. Add day-old rice and break up clumps with spatula. Spread into thin layer and cook 3-4 minutes without stirring to develop light crust.
Push rice to one side. Add beaten eggs to empty space and scramble until just set. Mix scrambled eggs into rice. Add frozen vegetables and cook 2 minutes, stirring occasionally.
Add soy sauce to rice mixture and toss to combine. Push rice to cooler edge of griddle to keep warm while cooking protein.
Cook vegetables: On medium heat zone, add 1 tablespoon each butter and oil. Add onions and mushrooms first, cook 3 minutes. Add zucchini, garlic powder, soy sauce, salt and pepper. Cook 3-4 minutes until tender-crisp. Move to rice zone to keep warm.
Cook chicken: Add vegetable oil to the hot zone (400-450°F). Place chicken cubes in single layer with space between pieces. Do not move for 2 minutes to develop golden sear.
Flip chicken pieces and add 2 tablespoons butter. Continue cooking 2-3 minutes, tossing occasionally, until chicken reaches 165°F internal temperature.
Pour prepared hibachi sauce over chicken. Toss continuously for 2-3 minutes until sauce thickens and caramelizes, coating chicken with glossy glaze.
Plate the meal: Divide fried rice among 4 plates. Top with hibachi chicken and vegetables. Garnish with sliced green onions and sesame seeds. Serve immediately with yum yum sauce on the side.