The trainer gave an early indication that the mush-fancied French duo could both by entered for the race on October 5th.
Montemarte has excited punters with a win at the Juddmonte Grand de Paris on Monday (July 14th), while Zarkavahas long attracted interest in the run-up to the Longchamp showpiece.
Speaking to At The Races, de Royer-Dupre commented: "I think it is possible for the two to run in the race.
"Monmartre can go on all ground, very soft won't be a problem for him. For Zarkava good to soft would be ok but softer may be a problem."
It is thought that Montmartre has matured since becoming unsettled in the preliminaries for the Prix du Jockey Club, also known as the French Derby.
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