Complex sentence: During the 1960s Marx offered its Elegant Models, a collection of not only Matchbox-like 1930s to 1950s style race cars in red and yellow boxes, but also airplanes, trucks, and, in the same series, metal animals boxed in a similar style.
Split into simpler sentences: During the 1960s Marx offered its Elegant Models, a collection of Matchbox-like 1930s to 1950s style race cars in red and yellow boxes. Also offered were airplanes, trucks, and, in the same series, metal animals boxed in a similar style.