A year after winning at Le Mans in the rain, Zarco sparkled on a dry, sunny afternoon at the Bugatti circuit on his LCR Honda.
After finishing fourth fastest in free practice in the morning, the 35-year-old had the French fans on their feet as he led qualifying with a time of 1 minute 29.907 seconds, 0.010sec ahead of Italian Fabio Di Giannantonio on a Ducati VR46.
Another Italian Francesco Bagnaia was 0.138 back on a factory Ducati.
"I'm really happy; the bike is much better and more competitive," Zarco said. "I've never felt this good on it this year."
"It's already high motion to lead the Friday practice in front of my crowd, over all after what I have lived last year, that is still a dream just coming here, knowing that I got the victory last year, and all the people are screaming for another one. So starting the Friday in first position, doesn't give any points, doesn't give any podiums, but it just gives us even more hope or even more possibility to dream," said Zarco.
Spaniards Alex Marquez (Ducati-Gresini), Joan Mir (Honda) and Jorge Martin (Aprilia) took fourth, fifth and sixth.
Italian Marco Bezzecchi (Aprilia), the World Championship leader, Spaniard Alex Rins (Yamaha) Japanese rider Ai Ogura (Aprilia-Trackhouse) and another Spaniard and Pedro Acosta (KTM) rounded out the top ten, who advance directly to the 12-man shoot-out for the the places on the first four rows of the grid.
Marc Marquez, on a factory Ducati, was nearly half a second behind Zarco and will have to try to secure one of the top two spots in Saturday's first qualifying session.
"It was a difficult day right from the start," said Marquez. "It was tricky to get a good feel for the bike. Even though things were getting better and better on the bike, I didn't manage to put in a very good lap. But the important thing is that the bike is working well. I just need to adapt my riding style and improve in all areas," said the seven-time World Champion.