Short answers, pulled from the story.
The Zond program was two distinct series of Soviet robotic spacecraft launched between 1964 and 1970. The first series used the 3MV planetary probe to explore Venus and Mars. The second series conducted uncrewed test flights around the Moon as precursors to a crewed Soviet circumlunar mission.
Zond 5 carried two Russian tortoises, wine flies, meal worms, plants, seeds, bacteria, and other living matter. Launched on the 15th of September 1968, the spacecraft completed a circumlunar pass and returned on the 21st of September 1968, making these organisms the first terrestrial life to travel around the Moon and return safely.
The Soyuz 7K-L1 spacecraft was launched on the Proton rocket, which was just powerful enough to send the Zond on a free return trajectory around the Moon without entering lunar orbit. The L1 was a stripped-down Soyuz consisting only of the service and descent modules.
Zond 9 was planned for July 1969 with cosmonauts Pavel Popovich and Vitali Sevastyanov, but it was cancelled and never flew. By that date, the Apollo 11 mission had already landed on the Moon, ending the Soviet hope of a crewed circumlunar first.
Four of the uncrewed Zond circumlunar test flights suffered malfunctions that would have injured or killed any crew aboard. Problems during re-entry were common across the majority of test flights from 1967 to 1970, and the Zond 1968B launch attempt resulted in the Block D stage exploding on the pad, killing three people.
Instrumentation aboard the Zond circumlunar missions gathered data on micrometeor flux, solar and cosmic rays, magnetic fields, radio emissions, and solar wind. Photographs were taken on multiple flights, and biological payloads measured the effects of deep space conditions on living organisms.