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