Belphemon is a powerful Digimon and he’s about as large as Zilla if not larger. That takes away Zilla’s big advantage from previous fights and it means that he is doomed. Zilla isn’t a long range fighter, but Belphemon can fly away and spam his energy blasts. He would also be able to defeat Zilla in a close combat fight thanks to his overwhelming power and chain abilities. Belphemon wins.