Bale scored twice – making it seven goals in nine games – while Isco matched the Welshman’s stunning second with a wonderful individual effort from the other side of the penalty area.
“It’s better to have everyone plugged in,” Zidane said at his post-match press conference.
“Then of course it will be a headache to select the team for the final.
“We had a great game and that was important. We were very professional, scoring six goals and playing a lot of football. We did very well.”
Bale has often incurred the wrath of Madridistas, especially when his impact has been affected by injuries.
But the 28-year-old received a warm ovation when he was substituted after 71 minutes, his double taking his league tally for the season to 15.
“He is very good, he has shown that,” Zidane said. “He was good at everything. I am happy for him. But the important thing is that we all arrive in optimal form.”
Goalkeeper Keylor Navas was another in the spotlight with Liverpool on the horizon. Navas made some important saves at 0-0 and earned praise from his French manager.
“I’m happy for him, for all the plaudits he has received,” Zidane said. “He saved us two or three times against Celta.
It gives us hope when Keylor can do this kind of thing.
“He is a very important player.”
Young Moroccan full-back Achraf Hakimi and Toni Kroos were also on the scoresheet, while Celta defender Sergi Gomez put through his own net.
Real’s emphatic victory leaves them three points behind second-placed Atletico Madrid going into the final weekend of the season.
Atletico kept their advantage by winning 1-0 at Getafe, but Diego Simeone’s side know they can not afford to falter at home to Eibar next weekend.
That is because Real – who conclude their season at Villarreal – have a vastly superior goal difference to their city rivals.
Celta Vigo dropped a place to 13th and the Galicians’ disappointing season is petering out.
“We wanted to be in those European positions but we have to think about next season,” striker Iago Aspas told beIN Sports Espana.
“The important thing is to take it little by little.”
Gareth Bale opened the scoring in the 13th minute and added a superb second with half an hour played. Isco then got in on the act with a curling finish two minutes later before Achraf Hakimi, an own goal from Gergi Gomez and Toni Kroos completed the rout.
Here’s how the Madrid players performed.
Keylor Navas 6 – Wasn’t tested to a great degree and only had the one save to make.
Achraf Hakimi 7 – Will Zidane give him the nod for the Champions League final? If he keeps playing like this – perhaps. Excellent in attack, taking his goal well and defended well.
Raphael Varane 6 – Calm and composed at the back. Cruised through the encounter.
Nacho 6 – Had a quiet outing as well. Tracked his runners well, always staying goal-side and covering for the marauding Marcelo.
Marcelo 7 – Superb in attack, creating several chances and was involved in the fifth goal as he played in Asensio. Little defending to do.
Casemiro 6 – Anchored the midfielder well, made five interceptions and had a shot well blocked at the death.
Toni Kroos 7 – Nearly perfect in possession and wound up with a goal and assist to his name.
Luka Modric 8 – Played some defence splitting passes and his ball for the opener was top quality. Unlucky to hit the upright in the closing stages.
Gareth Bale 9 – Had one of his best games this season and was a constant threat. Slotted away the opener after going clean through. Showed pace, skill and an amazing left peg for his second. Bale at his best.
Isco 7 – Sublime finish for Madrid’s third, curling his effort into the top corner. Did well to create from the left flank.
Karim Benzema 6 – Decent performance but had a much-needed goal ruled when an offside Isco touched it on its way in.
Marco Asensio 6 – Replaced Isco and fired across a ball that was turned in by the defender for the fifth.
Borja Mayoral 6 – Came on for Benzema and set up Kroos for the sixth.
Lucas Vazquez 5 – Introduced in place of Bale in the 72nd minute and didn’t make an impact.