Zidane, the director of football at Real Madrid, said the criticism was groundless and that Spain, who topped Group C unbeaten, remained favourites to going into Sunday's quarter-final against France.
Del Bosque's tactics of not playing a striker in the drawn match against Italy, drew criticism back in Spain but Zidane, who turns 40 today, backed Spain's style of play.
"One hears a lot said that Spain are not playing well or that they are playing without a straight No.9 or any other number of things, but they know very well where they are going and where they want to go," AFP quoted Zidane as saying.
France failed to get a positive result against eliminated Sweden ending up second to England in the table. "For me, the favourite is Spain, but at the same time, a one-off match such as this anything can happen, that is the beauty of football," said Zidane.
"We all known that Spain are the favourites, not just for this match, but also for the Euro." Zidane, who defied Spanish media predictions of being sent into early retirement by Spain in the 2006 World Cup quarter-finals by scoring in the 3-1 victory over them, said.
Zidane, who won the World Cup in 1998 and lifted the European Championship trophy in 2000, said the outcome of the match will be decided in midfield.
"Spain will look to have the most possession, it is their style of play and they do it well," he said.
"The French know this. Thus it will be in midfield where it will be decided," he said.