Complex sentence: Hong Jeong-do (born 1977) is the CEO of Joongang Media Network (JMnet) in South Korea, which has 37 subsidiaries and 26 brands of media platforms including newspapers, TV stations, magazines and a multiplex cinema Megabox chain.
Split into simpler sentences: Hong Jeong-do (born 1977) is the CEO of Joongang Media Network (JMnet) in South Korea. He is the chairman of JMnet (JoongAng Media Network), which has 37 subsidiaries and 26 brands of media platforms including newspapers, TV stations, magazines and a multiplex cinema Megabox chain.