"The very first bet ... was the beginning of the horrible, dangerous, crazy and uncontrollable behaviour," he said.
"I gambled 72 hours non-stop without eating, I gambled without thinking of the consequences."
The casino made him a VIP and Zhang said he was drawn into the meticulous treatment from casino staff and the luxurious VIP rooms.
"I generously offered tips of $100 or even $1000 to waitresses for a cup of coffee ... I was appreciative of all that the casino provided and in return I visited more frequently," said Zhang.
"It was madness, I lost $300,000 within two hours in Auckland and $400,000 within one week in Christchurch."
He borrowed money to fund his gambling habit, but said the special treatment ended when he lost all his money.
Zhang then sought help from Asian Family Services, which he said helped him through the toughest time of his life.
The 2018 National Gambling Study by AUT University found that migrants who gambled were at a higher risk of becoming a problem gambler compared with New Zealand-born Kiwis.
Although gambling participation continues to fall, the report said levels of gambling-related harm remained unchanged.
Professor Max Abbott, director of the Gambling Addictions Research Centre, warned that unless strong measures were taken, the rates of gambling participation and problem gambling among migrants were highly likely to increase.
"Asian people who do gamble are at very high risk of problem gambling," Abbott said.
This is despite the rates of gambling participation among Asians were lower than Europeans and others.
The study found that problem gambling prevalence rates among Asians are similar or slightly higher than Europeans.
Of those who reported having gambled in the past 12 months, around 14 per cent had a clinical or sub-clinical gambling disorder.
This was similar to Maori at 16 per cent, but much higher than Europeans at 8 per cent.
"A substantially higher proportion of Asian adults develop a gambling-related problem . . . this will increase if or when participation rates increase," said Abbott.
"In the future, it is highly likely that the prevalence of problem gambling and related harm will increase substantially in New Zealand's Asian population."
Overall, the total gambling population had dropped from 80 per cent in 2012 to 75 per cent in 2015.
The study found participation fell across most gambling forms including electronic gaming machines and casino table games.
But rates of problem gambling had not similarly dropped and gambling continued to also impact on Māori and Pacific people.
Ivan Yeo, Asian Family Services deputy director, said Asian cultural beliefs and values - such as "face saving" - exacerbated gambling harm.
"Individuals isolate themselves by refusing to attend social events for fear of being stigmatised, exacerbating feelings of shame and the experience of other harmful outcomes," Yeo said.
"Shame and stigma affect social and community connectedness, and severely impede help-seeking, early detection and future treatment."
Yeo said limited English ability, difficulties in finding jobs, being away from family and having significant spare cash and free time were among the reasons why many Asian migrants turned to gambling.
His advice for those who thought they had a gambling problem was not to try to fix the problem themselves and to seek professional help early.
* Name has been changed
Where to get help:
• Problem Gambling Foundation: 0800 66 42 62 or email help@pgf.nz
• Asian Family Services Helpline: 0800 86 23 42
• Mapu Maia (Pacific counselling team): 0800 21 21 22
