Zidane says the strikers appear to have recovered from their injuries and likely will "be fine to play" in the first leg in Manchester.
He said a final assessment would be made after the team's practice session later Monday.
Ronaldo was nursing a right thigh injury, while Benzema had a knee ailment.
Ronaldo missed Real Madrid's match against Rayo Vallecano in the Spanish league on Saturday because of his injury.
The strikers have scored 74 goals between them this season.
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