Complex sentence: Nintendo Entertainment Analysis and Development (EAD) was one of two companies involved with "Mario Kart 7", while its Software Development Department (SDD) was the team that actually handled the game's development.
Split into simpler sentences: Nintendo Entertainment Analysis and Development, better known as Nintendo EAD, was one of two companies involved with "Mario Kart 7". It was the company's Software Development Department (SDD) that handled the game's development.