Complex sentence: At the same time, Qing Dynasty invaded with formidable forces near Yunnan border at upper Burma which caused Hsinbyushin to reconsider Ayutthaya invasion and order mass annihilation of to avoid two pronged attacks from East and North in the future.
Split into simpler sentences: At the same time, Qing Dynasty invaded with formidable forces near Yunnan border at upper Burma. When Hsinbyushin heard the news of Qing invasion along the border, he ordered mass annihilation of Ayutthaya to avoid two pronged attacks from East and North in the future.