Complex sentence: Millennium Rodan looked more like the Showa version, it retained the ridges of bone on its chest from the Heisei era, it had only two horns again, and its color is similar to the Showa version.
Split into simpler sentences: Millennium Rodan looked more like the Showa version as it retained the Heisei era ridges of bone on its chest. It also had only two horns again, and its color is similar to the Showa version.