Complex sentence: The primary enemy for the Enterprise-D are the Romulans, the Cardassians and Jem'hadar for the Defiant and the Borg for "Voyager" although you have to fight also Species 8472 and the Kazon.
Split into simpler sentences: The primary enemy for the Enterprise-D are the Romulans. The Borg is the primary enemy for Voyager, although you have to fight also Species 8472 and the Kazon.