The Zond 5 was the first spacecraft to travel to the Moon and succesfully return to Earth.
The former Soviet Union planned a manned lunar landing with the new rocket N-1. This rocket had five stages and on top was placed a two-man Soyuz spacecraft.
The Zond was a modified Soyuz spacecraft used in the preperation of a Soviet manned Moon landing. This spacecraft was designed to swing around the Moon and return to Earth. On 18 September 1968 the Zond 5 succesfully did. It was the first spacecraft ever to fly to the Moon and back again.
The Zond 6 succeeded in doing the same objective only with a more gentile re-entry in Earth's atmosphere. Zond 5 carried a cargo of turtles and other animals, which did not survive the rough re-entry at 10-15 G-forces.