Complex sentence: A 50-minute artillery bombardment was followed by ZNG advance in three groups--the 57th Independent Battalion advancing from the south, the 127th Infantry Brigade from the north and the 1st Battalion of the 127th Infantry Brigade from the northwest.
Split into simpler sentences: A 50-minute artillery bombardment was followed by ZNG advance in three groups. The 57th Independent Battalion advanced from the south, the 127th Infantry Brigade from the north and the 1st Battalion of the 127th Infantry Brigade from the northwest.