Zakhar, the eldest son of Grigory Chernyshev, the first count Chernyshev and one of Peter the Great's generals, was enlisted in the Russian military service since 1735. After a diplomatic mission to Vienna and a period at court, he held the command of a Russian corps of approximately 20,000 soldiers in the Seven Years' War. It was one of his officers, Gottlieb Heinrich Totleben, who took hold of Berlin, the capital of Frederick the Great, in 1760.