Cornet, holder of the Open era women's record for consecutive major main draw appearances, had previously announced that she would bring the curtain down on her career after the tournament.
Cornet will still compete in the women's doubles and mixed doubles events before she walks away from the sport after almost 20 years as a professional.
"I was already in tears after Rafa Nadal’s match (on Monday). I’m in more tears now. Lots of emotions. I’ve been preparing myself for weeks for this moment but you’re never really ready when you have to say goodbye," Cornet said.
"I gave everything to tennis. I was just really lucky to have the life I’ve had. It took a lot of efforts and sacrifices and questioning yourself. There were lot of ups and downs. But what an adventure."
She gave it her all under the Court Philippe Chatrier roof on a rainy day in Paris but was no match for the Australian Open runner-up as she surrendered the opening set tamely and found herself a break down early in the next.
Zheng, who arrived at Roland Garros on the back of a run to the Rome quarter-finals and is bidding to claim her maiden major title, stepped up her game further to build a 5-1 lead before finishing the match off in style.
She hugged Cornet at the net as a small crowd at the main stadium rose to its feet and cheered for the local player.
"All of us, we will not forget you. I hope you will enjoy your life after tennis and be happy," Zheng said.
Zheng will next face either American Ashlyn Krueger or Germany's Tamara Korpatsch.
