Complex sentence: Its main competitors on the cable broadband Internet market are Numericable and VOO in the Brussels region, and Belgacom, the leader of the Belgian DSL market in the Flanders and Brussels regions.
Split into simpler sentences: Its main competitors on the cable broadband internet market are Numericable and VOO in the Brussels region. Its other main competitor is Belgacom, leader of the Belgian DSL market, in the Flanders and Brussels regions.