Complex sentence: During this same period, ESP began making the bodies and necks for Kramer Guitars and other manufacturers were using ESP as an OEM such as Robin Guitars, Schecter Guitar Research and DiMarzio.
Split into simpler sentences: During this same period of time, ESP began making the bodies and necks for Kramer Guitars. Other manufacturers using ESP as an OEM were Robin Guitars, Schecter Guitar Research and DiMarzio.