According to the Daily Mirror, Grimandi gave the French under-21 international a top mark after watching him in action in Ligue 1 for St Etienne.
The French club reportedly value Zouma at £12m, with Chelsea thought to be leading the race until Arsenal's recent interest emerged.
Because the report now claims the Gunners plan to challenge Jose Mourinho for his signature in January.
Wenger is believed to have met Grimandi to discuss January transfer targets earlier this month, with Zouma the top of the scout's shortlist.
The 19-year-old defender is reportedly keen on a move to the Premier League, with Chelsea, Arsenal and Manchester City the three English clubs credited with an interest.
He's regarded as one of the top young defensive players in Europe, although he's currently serving a 10-match ban for a nasty tackle that broke a Sochaux player's leg.
The priority for Arsenal next month remains a new striker, but Wenger is exploring options in defence as he knows it will difficult to keep a disgruntled Thomas Vermaelen at the club.
The Belgian international is desperate to play first-team football in a World Cup year - but like Chelsea counterpart Kevin De Bruyne, he's struggling for game time.