One of 12 kids, the Strikeforce light-heavyweight grew up on the San Pasqual Indian Reservation in California. Zwicker wouldn't back down to anybody and paid the price.
"I always made dumb decisions when I was younger," Zwicker acknowledged. "When I was 17 or 18, I made a really big dumb decision and I went to prison for it.
"But I had been going in and out (of detention) from 11 years old to that time."
He credits mixed martial arts for helping putting him back on the right path.
On Saturday, Zwicker (10-2) takes on Brazil's Guto Inocente (5-0) on a Strikeforce card in San Jose. The main event is the final of Strikeforce's heavyweight Grand Prix with Josh (The War Master) Barnett (31-5) facing Daniel (DC) Cormier (9-0).
But last year, Zwicker thought his fighting days were over. A test at a pre-fight physical indicated blood clots in the back of his head.
"When I first got the news I was devastated," he said. "I love fighting, it's one of those things I've always done. But I had to sit back and go 'OK, well do I want to see my kids get raised and be normal and be happy to be here. Or do I risk fighting and get injured?'
"What they thought is I had suffered from minor strokes in my sleep and it had caused air to get into my brain ... and caused blood clots.
"When they told me I'm like 'What? I feel better than ever. Who are you talking about?' It was scary, it was definitely scary."
To make matters worse, he was initially cleared to fight after the first test. Then a week before a scheduled Strikeforce Challengers fight last September, the doctors called him back and gave him the bad news.
It took a parade of visits to doctors and specialists before he was finally cleared in February.
"When an injury like this happens, doctors aren't just going to sign you off and say 'OK, you're OK to go.' It's a liability thing," said Zwicker who saw five doctors and four specialists.
It also cost a lot of money, with Zwicker forced to get his own medical insurance.
That wasn't cheap.
"No insurance plan would really cover me so I had to go under this pre-existing insurance plan, basically saying that I have a (medical) condition, which I didn't. But I had to do it just to get the insurance."
It was the latest setback in a life filled with detours.
Growing up, Zwicker estimates there were 15 years in which he was incarcerated for some part of the year.
"Being out a year was like my accomplishment and then I was like "Yes, I've been out a year.' And then I ended up doing a big term in state prison. That was a wakeup call for me. Just seeing how ugly it was in there.
"When I got out, I saw two of my close friends doing so well with training (MMA) and fighting."
He joined them, a decision would eventually help change his life.
His longest stint in prison was 44 months for uttering terrorist threats and assaulting a peace officer arising from an altercation with a sheriff's officer on the reservation.
Zwicker was sentenced to five years. The first, he said, was spent hating everybody. After two years, he started examining "what's it going to take for me to change and get out of this behaviour."
"Prison is an ugly place. You see a lot of ugly people in there. And there's a lot of good people too, but it seems like the majority of people, they love to prey on each other. They love to bully."
Race was also all-important. And while he hated the ugly cliques and having to watch who he talked to, he says he connected with "a lot of good Indian brothers" and got to refocus on his spiritual life.
He returned to prison just one more time after that long stint. He says he was jumped in his backyard by three men.
"One of the guys I hit, his eyeball came out and they violated me for that," he said referring to his parole. "Even though they were jumping me in my backyard, pulled a gun out. My wife was pregnant."
He spent nine more months behind bars and was paroled in 2006. "That was the last one."
He has stayed on the straight and narrow ever since, training at Team Quest in Temiculah, Calif. He credits his family and MMA training for the turnaround.
Today he lives with his wife, five-year-old son and four-year-old daughter in San Diego, about an hour away from where he grew up inland.
Zwicker started training full-time when he signed with Strikeforce, but has had to get another job recently to help pay for his medical costs. He works on the reservation, mentoring youth and coaching basketball and T-ball teams.
His goal is to lead by example and show kids that the tough guy act isn't necessary.
His first two fights, in 2003 and 2005, came between prison stints and he took them without a single day of training. "Went in there, beat them up and walked out."
His first fight, he was on the run from the law and took the fight for the money.
But his third fight, in 2007, he got out of prison and went to the gym and "trained, trained, trained."
He knocked out Ty Montgomery in 41 seconds.
The six-foot-two Zwicker is making his debut at 205 pounds for Strikeforce, although he has fought at light-heavyweight before.
His last Strikeforce fight, a win over Brett Albee in April 2011, was slated to be at light-heavyweight but was contested at a catchweight after his opponent failed to make weight.
The fight before was a knockout loss to heavyweight Lavar Johnson in October 2010.
Zwicker was holding his own against the much bigger Johnson until he took an uppercut to his nose at the fence. The fight was stopped via TKO in the first round.
"For a couple of weeks after I could just touch my nose and it would start pouring (blood)," Zwicker recalled.
It doesn't get any easier. Inocente, whose proper name is Carlos Augusto Filho, is new to North America but Zwicker says he's a world-class striker who has been a Shooto, Muay Thai and kickboxing champion.
"He has a lot more accolades that people know of," said Zwicker, who has trimmed down from 245 pounds for the fight.
"He's definitely not to be taken lightly."
But given his recent medical road, he is not complaining.
"I thought I was done. Not that I wanted to be done, but I'd rather be alive with my kids ... I was looking at the fight game at a whole other way than I am now.
"And they gave me another tough opponent. This guy is very, very good. So I've been motivated from the moment I signed on to fight this guy. He's pushed me harder than I've ever really trained, I think."