"This Zaching thing has helped fill that void with a lot of positive hope," said Zach's mother, Christine Lederer.

"He's telling everyone in that pose that he struck in the hospital, in his hospital gown, that he's determined, that he's going to get through this," said Bobo. "It's very moving to see people respond the way they are."

The fact that Zach is resolutely optimistic hasn't hurt, either.

'Be happy for me'

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In the firestorm of media attention he has received in the last two weeks, Zach has remained on message.

He knows people are worried, and he clearly doesn't like it. He seems more concerned for them than about himself. He knows the Zaching phenomenon has taken off because it is inspiring, and he wants his message to family, friends and fellow cancer patients to stay on point.

Worrying, Zach said, is a "waste of energy and time."

People have looked to Zach for how to respond to his diagnosis, and in that simple picture from his hospital bed, he has given them permission to be bold, a little cocky, unrelentingly strong.

"Don't be sad for me, be happy for me," Zach said Saturday, of the message he wants to convey. "Not many people get the opportunity to show how strong they are."

"There's no sense of, 'Oh, poor Zach,' and that's the way he wants it," Bobo said.

"Zachary, once again, has carried us through it," said his father. "He's extremely strong to take that outlook."

Indeed, it's an amazing outlook, especially when Zach, a broadcast journalism major, delivers it in person, his voice deep, his eyes unblinking, his gaze resolute.

He seems stoic but entirely genuine, and his composure isn't at all faked. It's something that has been won.

It is born out of Zach's experiences with cancer as a kid — "In a way, I've practiced beating cancer before," he said — and inspired by the many kids he now sees in the hospital, who, like he did at age 11, put on brave faces.

"Who am I not to fight when those kids are fighting their butts off?" he asked.

'Arrogant and confident'

This is certainly a fight, and Zach knows it. It's part of the reason why the self-described "sports fanatic" looks to one of his heroes, Muhammad Ali, for inspiration.

Ali was "mouthy, he was arrogant," Zach says.

The boxer was unconventional, leaning away from punches instead of putting up his arms. Zach takes a similar approach to fighting cancer, he said.

There are times when he stares at the mirror, defiantly, imagining he is challenging the cancer in his brain with an Ali-like bravado.

"When you have cancer, you kind of have to be arrogant and confident," he said. "Sometimes I look at the mirror like I'm talking to cancer. 'How dare you challenge me?' "

Zach's taken punches before. He knows there are more in store. "This is life and death," he said.

But he's ready, he said.

"Whatever they can throw at me, I'm ready for it," he said.

That's what people see in the picture that inspired Zaching, said his father.

"It's a resolute, determined look," John Lederer said.

"He tells me that he's aware that he is in a position in his life where he can inspire other people, and that he intends to use it, and indeed he is," Bobo said. "It's just fascinating to watch that from the position of an 18-year-old with a recurring malignant brain tumor, he is actually spreading joy in the community and the world."

That's it, right on message.

Raymond Kim's Tumblr page of Zaching photos, zaching.tumblr.com, has in part helped him and fellow Centennial graduates Kevin Barnes and Ella Lee raise funds for a 4,000-mile bicycling trip for cancer awareness they are participating in called 4K for Cancer. Those interested in donating can email Raymond at zaching27@gmail.com.