The US actress, who plays the lead role of recovering addict Rue on the popular HBO series, said she would remember Cloud for “all of the boundless light, love and joy he always managed to give us”.
Cloud, who played drug dealer Fezco O’Neill, died on Monday at the age of 25.
Sharing a black and white photo of him on Instagram, Zendaya wrote: “Words are not enough to describe the infinite beauty that is Angus (Conor).
“I’m so grateful I got the chance to know him in this life, to call him a brother, to see his warm kind eyes and bright smile, or hear his infectious cackle of a laugh (I’m smiling now just thinking of it).
“I know people use this expression often when talking about folks they love…’they could light up any room they entered’ but boy let me tell you, he was the best at it.
“I’d like to remember him that way. For all of the boundless light, love and joy he always managed to give us. I’ll cherish every moment.”
She added: “My heart is with his mother and family at this time and please be kind and patient as grief looks different for everyone.”
The actor was one of the breakout stars of popular TV series Euphoria, appearing in both series of the Sam Levinson-directed drama alongside Zendaya, Sydney Sweeney and Jacob Elordi.
Colman Domingo, who played Ali Muhammad in the series, was also among cast members posting tributes on Tuesday.
Sharing a picture of a smiling Cloud taking a selfie with the cast in his orange suit at the Euphoria premiere, Domingo wrote: “And that was his smile. That was him. May he rest sweetly in peace.”
He later wrote on his Instagram story: “Couldn’t be more real, original and sweet. Loved this kid. Always smiles.
“I hope this sensitive soul is at rest. Check on loved ones. Check on them.”
Meanwhile US actor Eric Dane, who plays real estate businessman Cal Jacobs in the show, shared a message on his Instagram story: “He was a one off. I’m truly sad.”
Cloud was most often in Euphoria scenes alongside his partner in crime Ashtray, played by Javon Walton.
Sharing a picture of the pair on Instagram, Walton wrote: “Rest easy brother” and later “forever family.”
Meanwhile on Twitter, Kathrine Narducci, who played Cloud’s on-screen grandmother Marie O’Neill in Euphoria, described him as a “gentle beautiful soul” who “exited to soon”.
Storm Reid, who plays Zendaya’s on-screen younger sister Gia Bennett, shared a clip of Cloud laughing on the show to her Instagram Story, captioning it: “The tears just won’t stop.”
Alexa Demie, who plays Maddy Perez, posted a heartbreak emoji on her Instagram Story.
In a statement shared with US outlets, Euphoria director Levinson said: “There was no-one quite like Angus. He was too special, too talented and way too young to leave us so soon.
“He also struggled, like many of us, with addiction and depression. I hope he knew how many hearts he touched.
“I loved him. I always will. Rest in peace and God Bless his family.”
In a statement following his death, Cloud’s family said he had “intensely struggled” with grief after recently burying his father.
“The only comfort we have is knowing Angus is now reunited with his dad, who was his best friend,” the statement said.
“Angus was open about his battle with mental health and we hope that his passing can be a reminder to others that they are not alone and should not fight this on their own in silence.
“We hope the world remembers him for his humour, laughter and love for everyone.”
A fortnight before his death, Cloud posted a picture of his father wearing a red tracksuit, captioning it: “Miss u breh.”
Cloud was plucked from obscurity to land his role in Euphoria, after being spotted walking down the street by a talent scout in New York.
He was recently cast to co-star in Scream 6.