Complex sentence: Centered at the first to third and eighth to tenth ranks of the board are two zones, each three points by three points, demarcated by two diagonal lines connecting opposite corners and intersecting at the center point.
Split into simpler sentences: Centered at the first to third and eighth t9 tenth ranks of the board are two square zones. The three point by three point zone is demarcated by two diagonal lines connecting opposite corners and intersecting at the center point.