World number 23 Zhang had to battle hard to make it through to his fourth ranking final.
Zhou, who beat England’s Ali Carter in a decider to reach the last four, was well placed to win the final frame but ran out of position on the blue when he looked set to clear up for victory.
The 28-year-old Zhou then potted the cue ball in off the blue during a safety exchange and Zhang, 34, cleared up to seal the win.
“I was nervous in the last frame and I’m still nervous here,” said Zhang.
“My hands are shaking. It is very exciting. I just hope tomorrow is a great final.”
Zhang, whose only ranking title came at the International Championship in 2023, will go into Sunday’s final as an underdog against world number eight Zhao.
The 28-year-old Zhao has been searching for the irresistible form that carried him to victory over three-time world champion Mark Williams in the Crucible final last May to win the sport’s biggest prize.
The highlight moment of his season so far came at the Riyadh Season Championship in November when he beat Neil Robertson to take the title.
Zhao went into the interval level at 2-2 against Xiao but won the next three frames and ended his opponent’s hopes of a fightback by producing a break of 121 – his first century of the match – to seal victory.