Complex sentence: The four female members of the group along with a new member, Seo Eunkyo, became 5dolls; the six male members plus one new member, Shin Jong Kook, debuted under the name Speed the year after.
Split into simpler sentences: The four female members of the group along with a new member, Seo Eunkyo, became 5dolls. The five remaining male members, plus Jongkook, debuted under the name Speed the year after.