It was the World No.50 who came out of the gates, as she totaled five winners across the first two games as she was quick to settle in.
"I'm really happy I can make the quarterfinals and play on Court 1 against the, yeah, former No. 1," Zhang said in defeat.
"Today I had a really good start. I make, like, 4-1, 40-15 I think. Yeah, I try my best, play – try to play more winners. After the 4-1, I made more mistakes , I think.
"She really does get good rhythm after the few games. I … did nothing wrong, I just tried my best. Anyway, [I'm] really happy this year [with] Wimbledon."
Halep trailed 4-1 in the opening set, but came through what proved to be a crucial sixth game – where she saved four break points which would have seen her trail 5-1 – to win three straight games to level.
"Winning that … I really thought that's still in the set. If the score would have been like, 5-1, I think the set would have been gone," Halep said.
"I just kept motivating myself and believed that I can turn it around."
Halep later won the first set in tiebreak, winning five of the last seven points to claim her first set from Zhang in seven years, and eased through the second set behind a pair of late service breaks.
She continued: "I really think that she always played well with me at least when she was really tough to return the balls and get the rhythm.
"I knew that I had to go back and forth too far from the court, so much more aggressive. She serves very, very well. She hits the ball strong.
"I think she improved in forehand so. It's strong on both ways. I think she has a great game."