Questions and answers
Q: Is it possible to cumulate two charge bonuses in a single attack ?
A: Yes, indeed. If the two cavalry units have charged the same unit and if the combat situation allows one of them to support the other, then both gets the charge bonus.
Q: My charge was successful and the enemy retreated behind a stream. What will be my bonus in the attack ?
A: First the CS benefits from the charge bonus, then this value is halved since the enemy is protected by the stream.
Q: Can a cavalry unit charge several times in the same turn ?
A: Nothing forbids that. A unit is forced to stop its movement only if it enters an enemy zone of control. Suppose for instance that the target of a charge is behind a stream, and that the charge fails. Then the charging unit is out of any zone of control and may carry on its movement.