Complex sentence: In 2006, he sold his interest in Thayer, which was renamed Nex-Tech Aerospace, and became president of Sentry International, an oilfield equipment company, which was also a partner with Koch Industries.
Split into simpler sentences: In 2006, he sold his interest in Thayer, which was renamed Nex-Tech Aerospace. He became the President of Sentry International, an oilfield equipment company, which was also a partner with Koch Industries.