While speaking with PEOPLE for their latest issue, the TV host recalled Zen's heartbreaking journey with a rare brain cancer -- from the moment he and the infant's mother, Alyssa Scott, knew something was off, to their decision not treat Zen with chemotherapy, to Cannon's final moments with his son, who passed away on December 5.
Cannon, 41, and Scott, 28, welcomed Zen in late June. A few days following the birth, the two became concerned after noticing that their "super calm" newborn was having some breathing issues.
"It sounded like he had fluid in his lungs, like a sinus infection or something," Cannon told PEOPLE. "[The doctors] didn't think it to be anything too concerning." However, he said a few weeks later the doctor said that Zen's head was "growing a little two quickly."
And in August, when Zen was only 2 months old, Cannon and Scott received the sad news of their baby boy's cancer diagnosis. Zen was diagnosed with a high-grade glioma, a rare form of brain cancer. Dr. Joffre E. Olaya -- a pediatric neurosurgeon at Children's Hospital of Orange County (CHOC) who treated the infant -- told PEOPLE that the high-grade gliomas, which are tumors found in the brain and spinal cord, "can grow and spread quickly" and "are very difficult to treat."
Although doctors put a shunt in Zen's skull to drain the fluid, his brain tumors unfortunately continued growing.
"We started asking, 'Is there a way to prevent this? If not, how long do we have?'" Cannon said. "The conversations quickly turned to, 'How can we give him the best life for the time that he does have?' It could be weeks, it could be months, it could be years."
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The "Masked Singer" host went on to explain why he and Scott decided against treating Zen with chemotherapy or have him undergo more invasive procedures.
"We were having quality-of-life conversations," said Cannon, who was previously treated with chemotherapy for his lupus. "We could have had that existence where he would've had to live in the hospital, hooked up to machines, for the rest of the time. From someone who's had to deal with chemotherapy before, I know that pain. To see that happen to a 2-month-old, I didn't want that. I didn't want him to suffer."
He shared that they tried to keep Zen "as happy as he could possibly be."
"We focused on Disneyland, our favorite place," Cannon told PEOPLE. "Every month we would celebrate his birthday, just really seeing it as a victory every time he had a milestone that he was still here with us."
However, comedian said Zen's condition severely worsened over Thanksgiving weekend, describing it as the "scariest thing I've ever experienced."
"You could tell he was struggling," he said. "He was gasping for air. We'd wake up, and he wouldn't be breathing for maybe five to 10 seconds at a time, and then he'd let out a huge gasp. You could see it frightened him."
As he previously shared on his talk show, "Nick Cannon," Cannon held his son for the last time at the beach. "I was like, 'We have to watch the sun rise and just be there with him one last time,'" he told PEOPLE. "It was beautiful."
Zen died on December 5. "I see it as a blessing that I got to be there," Cannon recalled. "Alyssa says, 'I think he was just waiting for you.'"
Reflecting on his son's heartbreaking death, Cannon said, "We had a short time with a true angel. My heart is shattered. I wish I could have done more, spent more time with him, taken more pictures. I wish I could have hugged him longer."
"He was the most loving baby," he added. "I look at being his father as a great privilege."
Scott echoed Cannon in a written statement to PEOPLE, saying "it was a privilege being Zen's mommy." She continued, "It's so beautiful and encouraging to see even complete strangers being touched and moved by Zen's light. Zen's spirit and light will shine bright forever."
Zen was Cannon's youngest child and was born just nine days after he welcomed twins Zion and Zillion with Abby De La Rosa earlier this year. He also shares two children with Brittany Bell -- 11-month-old daughter Powerful Queen and 4-year-old son Golden -- and 10-year-old twins Moroccan and Monroe with Mariah Carey.