Ex-boxing champ Zab Judah beat people up for a living ... but now he's got another job, assisting elderly patients with dementia, and helping teach a nursing class.
Judah -- a 4x boxing champ -- is working at an adult day care facility during the day, and helping teach a nurses assistant class by night ... all the while still training as a pro fighter.
Teberah Alexander -- the director at Excelling Nursing Academy who also runs the day care facility -- tells TMZ Sports that Judah recently graduated the nurses assistant class (he's now CPR certified, and First-Aid trained) ... and now actually helps teach a class of students studying to get certified.
Alexander says Zab primarily works with people with dementia and Alzheimer's ... and has developed a bond with the elderly patients.
She says Zab does everything from catheters to taking vitals.
it's no secret that Zab has had his fair share of trouble in the past ... but we're told that Judah has changed his life, and has been a favorite of patients, staff and students at the nursing facility.