The attacking midfielder has become a peripheral figure under head coach Zidane and last month his agent and father, Francisco Alarcon, suggested he is ready to try a new league amid reports Arsenal, Manchester City and Everton are monitoring his situation.
Since the start of the 2018-19 season, Isco has started just 29 times in LaLiga, while he has been named among the starting XI only three times this campaign.
In those games, Isco has failed to score or provide an assist, but he has created four chances for team-mates and has a pass success rate of 87.56 per cent.
Zidane was reported to have told Isco he should seek pastures new in January but says he will remain a big player for Madrid this term.
"Isco is going to be an important player, it is true that he is not playing much and I am not giving him the opportunity to show the player that he is," he said when previewing Tuesday's clash against Athletic Club.
"I feel sorry for my players and I will never forget what I have experienced with them.
"He has to work hard to get another chance, but what is being said [in the media] I can't respond because we don't control it."
Zidane's own future was said to be under threat after defeat to Shakhtar Donetsk in the Champions League left their chances of qualifying for the last 16 hanging in the balance.
But victory over Sevilla preceded 2-0 triumphs over Borussia Monchengladbach and rivals Atletico Madrid, to secure a place in the knockout stages of Europe's premier competition and reduce the deficit to Atleti in LaLiga.
Asked about the upturn in fortunes, Zidane said: "I don't aim to prove anything, I take advantage of every moment I'm here.
"I have fantastic players and there is nothing left but to keep working.
"It has been a very good week and we have to continue at that. The games are hard and there is no time to rest, just to continue in the same way.
"We are not going to change anything, we know that we have to always be the best, but there is an opponent and sometimes it is difficult to put the opponent in danger all the time.
"But we are good and we can show consistency. For us it has changed nothing."
Zidane also said veteran full-back Marcelo has to keep showing what he can do after falling out of favor to Ferland Mendy in recent weeks.
"It is true that he has played less, we know what he can give us," he said.
"It is true that Ferland has played very well, it is true that [Marcelo] has not played much lately.
"He is training very well and has to continue what he is doing. It is true that he hasn't had a chance lately but it's not his fault, we'll see what happens later."