The 36-year-old downed Kristyna Pliskova of the Czech Republic 7-6 (7/4), 6-4 to register her first victory at the majors since her 2017 Australian Open triumph.
She gave birth on September 1, then dealt with complications related to a pulmonary embolism.
I call it like my Wakanda-inspired cat suit.
"I feel like a superhero when I wear it", she added.
"I'm always living in a fantasy world. I have given tennis so much, and tennis has actually given me a lot, and I couldn't be more grateful", Williams said.
After beating Williams in the 2016 final, Muguruza's title defense was ended in the fourth round previous year.
The five-time Grand Slam champion insists she loves being challenged by all different kinds of opponents as she looks to claim a third title at Roland Garros.
Oil falls on possibility that Opec will ease output cut Renewed U.S. sanctions following the cancellation of the Iran nuclear arms deal may also remove supply from the market. For Russia, stability is more important than a short-term significant growth in price, he said in the interview.
"I did everything possible with my team to get us in a position to be able to play today. I was terrified, and it was a whole new kind of fear". "It makes me laugh that many parents only talk about the lovely, but it's also hard and there are sacrifices".
She explained: "For so many years, I defined myself in just one way: by success, by championships, by making history".
Williams conceded she was unable to fully gauge her level in her first major championship outing in 16 months against the big-serving Czech, such was the soaring ace tally and lack of extended rallies in their first-round tussle. Two years has been a really long time since my last match on clay but I feel good.
"I'm just happy to win a match here, " Williams told the crowd in Court Philippe Chatrier. "Yeah, so I think there are definitely some differences, but there is a lot of similarities, as well". "The connection that it gives me to Olympia, it's been one of the most magical things I've ever experienced".
"I'm concerned how that's going to work out for me, because normally in Grand Slams I do spend a lot of time at the site".
"I have been wearing trousers a lot when I play so I can keep the blood circulation going".
She had deliberately held back from a return, skipping Rome and Madrid, in order to make sure she was ready to compete on what is her least natural surface, training at the academy belonging to her coach, Patrick Mouratoglou.