Zhao had struggled in ranking events this season, failing to go past the second round in nine of the 11 tournaments he entered.
But he had been successful in non-ranking events, winning the Riyadh Season Championship in November and making the last four of the Shanghai Masters and Champion of Champions.
He hit successive breaks of 145 and 130 in the opening session but 34-year-old Zhang, chasing a second ranking title in his fourth final, knocked in four breaks of more than 50 as the first session was shared 4-4.
Zhao raised his levels further in the evening session, scoring heavily to take three of the next four frames, opening a 7-5 lead with a break of 111.
World number 23 Zhang was on for a maximum 147 break in the 13th frame after potting 10 reds and nine blacks, but he broke down on 73.
Zhao restored his two-frame advantage with a 134 break and hit 65 to move within one of victory before sealing the win and £180,000 winner’s prize with a 131 clearance.
It proved a fitting finish to what has been a landmark tournament for Chinese snooker, producing the first all-Chinese semi-finals at a ranking event, while nine of the last 16 in Hong Kong hailed from the nation.