The 28-year-old playmaker, who has fallen down the LaLiga champions' pecking order, has been linked with moves to Manchester City and Arsenal.
''All the players who are part of this squad," insisted Zidane after Saturday's 1-1 draw against Villarreal.
"We're not going to talk about possible departures. Isco now is a Real Madrid player and is our player. And nothing else to talk about.''
Isco has struggled to break into Zidane's starting line-up this season, having played just 260 minutes in LaLiga so far this term.
The Spain international was recently overheard complaining to teammates about his lack of playing time from the bench during Madrid's win over Barcelona.