Real Madrid's assistant coach is pleased for the 32-year-old who has struggled to keep his place in the first team at club level
Casillas, who recorded his 150th cap against Finland on Friday, has found the going difficult at the Santiago Bernabeu since he broke his hand earlier this year and lost his place to Lopez in goal while under former coach Jose Mourinho.
New boss Carlo Ancelotti has continued the precedent set by Mourinho, with Lopez starting all Liga games in goal for los Blancos, but, Zidane is pleased that Casillas' place as Spain No.1 has not been affected.
"I am glad that Iker will be holder. He is a great goalkeeper," Zidane told reporters.
However, the former World Cup winner was giving nothing away on whether Casillas would be able to reclaim his spot in Ancelotti's side.
He added: "We will see what happens at Madrid."
Casillas is in line to play against Chile for Spain on Tuesday before returning to club duties where Madrid's next match is against high-flying Villarreal on Saturday.