Complex sentence: The most important vector through which French spread since colonization ‌--either French or Belgian‌--is without a doubt the education system, may it be in French only (Côte d’Ivoire, Gabon) or bilingual (Togo, Rwanda).
Split into simpler sentences: The most important vector through which French spread since colonization-either French or Belgian-is without a doubt education. May it be only in French (Côte d’Ivoire, Gabon) or bilingual (Togo, Rwanda).