Real Madrid have already spent over £250million on new players this summer.
Eden Hazard was the most expensive, joining for an initial £88m from Chelsea last week.
But Zidane still wants Paris Saint-Germain sensation Kylian Mbappe and Manchester United midfielder Paul Pogba.
ESPN’s Sid Lowe claims a deal for Mbappe in this window is extremely unlikely but there is slightly more of a chance of Pogba joining.
However, he says Real Madrid must sell a number of high-profile players first before they can even think about signing either of those players.
Zidane would like to sell the likes of Gareth Bale and James Rodriguez but Lowe says that is easier said than done.
“[Real’s new signings are] the recognition or the idea at least that they will recuperate significant amounts of money,” Lowe told ESPN FC.
“Obviously you mentioned James [Rodriguez] and Gareth Bale as theoretically the players that would generate the most money.
“But you’ve also got to look at people like [Marcos] Llorente, [Dani] Ceballos, Keylor Navas.
“I wouldn’t be at all surprised if maybe one or two other slightly bigger players, if an offer came in for someone like Luka Modric, I wouldn’t be massively surprised if they at least listened to it.
“Real Madrid know they need to recover money, not least because Zidane at least would like this to continue.
“He would like a couple more players.
“Everybody knows, it’s pretty much an open secret now, that he would very much like them to get Mbappe.
“I think realism suggests that just doesn’t happen.
“Everybody knows that he would very much like to get Paul Pogba.
“Realism suggests that probably doesn’t happen but maybe is not quite as downright impossible [as Mbappe].
“But of course for Madrid to do that they will need to generate money and they know this is going to be incredibly difficult to do.”