Bring rice and water to a boil in a small saucepan. Cover, turn heat to low and cook for 18 minutes; remove from heat and rest covered for 10 minutes.
Toss radishes with vinegar, sugar and salt and leave for 20 minutes while cooking. Mix pear, soy sauce, ginger and garlic in a separate bowl.
Heat half the neutral oil in a large skillet over medium-high heat. Cook zucchini for 6 to 8 minutes, turning occasionally, until browned and tender; transfer to a plate.
Heat the remaining oil in the skillet. Press beef into a thin layer, sear for 3 minutes and break into small crumbles; cook for 3 to 4 minutes more, until no pink remains and the beef reaches 160°F.
Stir the pear mixture into the beef and simmer for 4 to 5 minutes until its excess liquid evaporates. Remove from heat and stir in sesame oil.
Fluff rice and divide among four bowls. Add beef, zucchini and drained radishes, then scatter the measured sesame seeds over the beef.