The Wales international, 30, was left out of Real's 3-1 preseason defeat by Bayern Munich in Houston, the US, BBC Sport reported.
Speaking after the game, Zidane said, "We hope he leaves soon. It would be best for everyone. We are working on his transfer to a new team.
"I have nothing personal against him, but there comes a time where things are done because they must be done."
Bale, who has three years left on his Real contract, has won the Champions League four times since his £85m move to Madrid from Tottenham in 2013 – a world record deal at the time.
He has been linked with Premier League sides Manchester United and Spurs, German champion Bayern and also a move to the Chinese Super League.
Injury problems have limited the Welshman to 79 La Liga appearances in the past four seasons. He played 42 matches for Los Blancos last term, half of those as a substitute.
"I have to make decisions. We have to change," Zidane added.
"The exit is the coach's decision, and also of the player, who knows the situation.
"The situation will change, I do not know if in 24 or 48 hours, but it will – and it's a good thing for everyone."
Bale ended last season on the bench as Real endured its poorest domestic campaign in 20 years, with 12 defeats, 68 points and a third-place finish 19 point behind champions Barcelona. The Madrid giant was also knocked out of the Champions League by Ajax in the last 16.
Zidane returned to the Bernabeu in March to become the club's third coach of the season.
As well as four Champions Leagues, Bale has won one La Liga title, a Copa del Rey and three UEFA Super Cups and Club World Cups during his time at Real.
He has scored more than 100 goals for the Spanish side but has reportedly been nicknamed "The Golfer" by his teammates, and goalkeeper Thibaut Courtois also said Bale did not attend a team meal because he did not want to miss his bed time.
Meanwhile, Bale's agent branded Zidane a "disgrace" after the Frenchman revealed that the La Liga giant was ready to offload the Wales star.
"Zidane is a disgrace, he shows no respect for a player that has done so much for Real Madrid," Bale's agent Jonathan Barnett told AFP.
Asked whether Bale is close to leaving Madrid, Barnett added, "We are working on it".
After Zidane's reappointment, Bale played 90 minutes in just three of the remaining 11 matches, was left out completely four times and frequently substituted when he did play.
He was denied a chance to say goodbye at the end of last season when he was left on the bench in a 2-0 loss to Real Betis that saw Zidane's side submerged with boos and whistles.
Bale joined Real Madrid to much fanfare, a blockbuster transfer fee and a big salary that may prove to be an obstacle for all but the richest teams.
He has three seasons left on his deal.