Williams, who was battling depression, was found dead at his home of an apparent suicide. He was 63. In his final Instagram post on August 1, the actor had wished Zelda a happy 25th birthday.
He had also posted a picture with this caption "tbt and Happy Birthday to Ms Zelda Rae Williams! Quarter of a century old today but always my baby girl. Happy Birthday @zeldawilliams Love you!"
Zelda today posted the poem: "You - you alone will have the stars as no one else has them... In one of the stars I shall be living. In one of them I shall be laughing. And so it will be as if all the stars were laughing, when you look at the sky at night ... You - only you - will have stars that can laugh," she qouted Saint-Exupery before adding, "I love you. I miss you. I'll try to keep looking up."
Williams death stunned his friends and admirers in the acting community.
"I could not be more stunned by the loss of Robin Williams, mensch, great talent, acting partner, genuine soul," comedian Steve Martin tweeted.
Actress Sarah Michelle Gellar, who worked with Williams on TV show 'Crazy Ones', said, "My life is a better place because I knew Robin Williams. To my children he was Uncle Robin, to everyone he worked with, he was the best boss anyone had ever known, and to me he was not just an inspiration but he was the father I had always dreamed of having."
Actor Jeff Bridges, his co-star in 'The Fisher King', said it was difficult for him to attend the premiere of 'The Giver' after hearing the news about Williams death.
"I am filled with such mixed emotions tonight. It's very difficult for me to be here with all these emotions and feelings - wonderful, I must say, but as with many elements in life, there is an underbelly, and we're losing a dear, dear friend, Robin Williams. Such a brilliant human being. My heart goes out to his family... I feel Robin coming in now, he says, 'Get on with it, Bridges! On with the show!'"
Meryl Streep said, "It's hard to imagine unstoppable energy stopped. Williams was such a generous soul."
"I promise you, if he were onstage, he'd want the party to continue and continue and continue. He is well missed and well loved, and whatever the circumstances are, he was a giant in our industry and more importantly, a great man," said Harvey Weinstein, who produced 'Good Will Hunting'.
Lady Gaga tweeted: Rest in Peace+Laughter Robin Williams. Perhaps this tragedy will shed light on the seriousness of depression. You made us all so so happy."
Tom Hanks' actress wife Rita Wilson, who was a friend of Williams, added, "I will remember your warmth, kindness, unparalleled talent, generosity, beautiful children, Robin Williams."
"Robin Williams made the world a little bit better. RIP," Steve Carrell said.
Ellen DeGeneres: "I can't believe the news about Robin Williams. He gave so much to so many people. I'm heartbroken.
"RIP Robin Williams. Such a loss. He will be gone but never forgotten. #RIPRobinWilliams," tweeted Morgan Freeman.
Williams is best remembered for his performances in 'Mrs Doubtfire', 'Dead Poets Society', 'The Fisher King' and 'Good Morning, Vietnam'.