Complex sentence: Due to a realignment in the Eerste Divisie, the Tweede Divisie would be expanded from one Group to two, while the Eerste Divisie would become one league instead of two, meaning many teams would be relegated to this league next season.
Split into simpler sentences: Due to a sanitation in the Eerste Divisie, the Tweede Divisie would be expanded. The Eerste Divisie would become one league instead of two, meaning many teams would relegate to this league next season.