Murphy set the tone in the opening session, overturning a 3-0 deficit to lead 5-3 with five consecutive frames built on composure rather than heavy scoring.
Zhao had started sharply, compiling a 122 and adding a 57, but a series of missed chances allowed Murphy to take control, winning several tight frames on the colours.
Zhao hits back to level
Zhao gradually worked his way back into the match and refused to let Murphy pull away, even as the Englishman threatened with breaks of 59 and 90.
A key moment came when Zhao cleared to stay in touch before producing a superb 117, his eighth century of the tournament, to draw level.
The defending champion then took the final frame of the session to complete the recovery and leave the match finely poised at 8-8.
Allen and Hawkins remain inseparable
On the other table, Hawkins had earlier established a 5-3 lead, punishing errors by Allen with breaks of 114, 72 and 69.
Allen responded in the second session, compiling centuries of 138 and 131, the latter marking the 700th century of his career, while Hawkins matched him with a superb 140 clearance.
Frames were shared throughout, as neither player was able to gain a decisive edge.
In a tense closing frame, Hawkins looked set to move clear but faltered late on, allowing Allen to step in and secure an 8-8 scoreline.
Both quarter-finals now head into their concluding sessions with their outcomes still firmly in the balance.