But although he expects a "difficult" game, the former World Cup victor said Real expect one result only. "The Champions League is always an extraordinary motivation".
"It's never easy here".
Bale said: "My mindset was to stay as long as I can - I read Mark Hughes saying that when he came over he was already thinking about going home". "Now he is contention to play, we will see his condition ahead of the game".
"We're more than ready".
When all three players have played for Los Blancos during this season, Madrid have managed to win just nine out of a possible 16 matches, drawing six and losing one game. "I'm sure we will have to suffer at times but we are ready for it", he added. Defending champion Madrid won the first leg 3-1.
But goals by Karim Benzema, Toni Kroos and Brazilian midfielder Casemiro offered a stark reminder of Real's European pedigree.
The Spanish giants will be keen to score an away goal, which could be an ideal scenario for Real Madrid, meaning, Napoli will have to score four goals.
But Zidane appears to have covered all the bases.
Napoli appeared to heed the warning as they reasserted control, with Kalidou Koulibaly heading over and Mertens striking a shot against the outside of the post. Surprisingly the last team to keep them out were Manchester City in last season's semi-final first leg.
"Our world champions are our supporters and tomorrow all of Europe will see that".
He also hit a post late in the first half after Cristiano Ronaldo had done the same for Real.
Ronaldo sat out the weekend's 4-1 victory over Eibar due to a minor injury concern, while Gareth Bale is suspended for domestic matches thanks to his red card against Las Palmas.
In red-hot from prior to their first-leg clash with Madrid, things have gone downhill for Maurizio Sarri's men since then.
Azzurri captain Marek Hamsik said earlier: "There's still everything to play for".
"In football you have the chance to change the script every three days".
Bayern's opening goal in that game came after just 11 minutes and Arsenal have a strong recent trend of giving away a goal just as the game is getting started.