By the time he was 18 months old, it was obvious enough that Amy Zang’s little boy Brandon had some challenges to address.

At first, doctors diagnosed Brandon as having a developmental delay. Then autism. Then attention deficit hyperactivity disorder, oppositional defiant disorder and pervasive developmental disorder. Then back to autism.

Those were difficult and confusing times for Zang, who had emigrated from her native Vietnam to Hawaii with her soon-to-be ex-husband and was already struggling to learn English and to find support in her new home.

"I’m not a doctor," Zang said. "But I knew my son."

When Brandon struggled to learn the alphabet, Zang taught him the piano, assigning letters to different notes until Brandon could sing the entire alphabet.

Doctors said Brandon would have difficulty dealing with public situations. So Zang took him out every day, rotating between McCully-Moiliili Public Library, the Hawaii State Library and Lili­ha Public Library, just so he could get used to being around other people.

That was just the beginning. To focus Brandon’s near-limitless energy, Zang found free or low-cost programs in which Brandon could learn swimming, gymnastics, judo and aikido. And whatever Brandon did, Zang had to do, too.

"When he was taking gymnastics," Zang recalls, laughing, "I was sore every day."

When Brandon was 8, he suffered a debilitating seizure that wiped out four years of memory and left him partially paralyzed.

Needing an outlet, Zang took out a series of student loans and went back to school, eventually earning bachelor’s degree in math and Chinese, and a master’s degree in math.

She also joined a USTA tennis program, whose members have embraced Zang and Brandon like family.

Brandon, now 14, enjoys a busy schedule of classes at Assets School (he’s a math whiz like his mother), scouting, sports and martial arts.

Zang recently got a job renting audio tours at Pearl Harbor. She enjoys meeting new people every day, even if the job isn’t the typical career path for someone with an advanced degree in mathematics.

"I’m not a doctor," she said. "Personally, I’m not very successful."

She couldn’t be more wrong.

Reach Michael Tsai at mtsai@staradvertiser.com.