Raoul said:

"Didn't it reduce the heat load by sending the spacacraft back into
space before re-entering defnitely? It's like aerobraking first, then
entering the earth's atmosphere, next. And that way, they could
send the spacecraft to a very precise place."

First a nit-pick: "Heat load" is time integrated heat flux. If you want to minimize heat load then you hammer into the atmosphere as close to normal incidence to the local horizon that your vehicle's structure and thermal protection system can tolerate. With a manned vehicle, you don't want to decelerate more than 4 gravities. This dictates a shallow entry angle and high heat loading.

I have been told the Zond double skipped because of the Soviet political requirement that manned vehicle's always land within the Soviet Union. Supposably the celestial mechanics of lunar return dictated a double skip if the vehicle was to land within the Soviet Union. Double skips are NOT desireable in terms of thermal protection. The problem is that during the first skip, a heat pulse is deposited within the heat shield. This deposited heat causes a temperature wave to slowly work its way through the heat shield towards the crew. The result is the temperature of the inner wall of the pressure vessel is slowly rising. With the Apollo Command Module (CM) the temperature of the inner wall could get hot enough to burn an astronaut's feet while the CM was hanging from its parachute. Fortunately, the astronauts were suspended in their couches from the top of the CM's inner wall and had no direct contact with lower inner wall. The CM then landed in the ocean where it dumped the residual heat, quickly cooling the heat shield. Had the CM landed on the ground, the crew would have experienced a hard landing and then needed to get out of the CM fast before it got too hot. The Space Shuttle has a similar problem. If you watch a Shuttle landing, you'll notice a big truck that drives up to the rear Shuttle immediately after landing and attach numerous hoses. Some of those hoses pump in freon refrigeration to cool down the Shuttle's structure. I was told if a Shuttle did an emergency landing far from one of those trucks, the crew needed to get out of the Shuttle fast and Shuttle's hardware would then cook to a golden brown.

Anyway, double skips are a bad idea for a crewed vehicle because that heat pulse can have a chance to work its way through the heat shield and cook the crew.

Gary