Zaidpour denied favourite backers a success as he got the better of Voler La Vedette in the John Mulhern Galmoy Hurdle at Gowran Park.
Unsuitable ground conditions at Leopardstown prompted Colm Murphy to send Voler La Vedette to Gowran rather than wait for Sunday's BHP Insurances Irish Champion Hurdle but Zaidpour proved too good on the day under a determined Ruby Walsh.
Willie Mullins' charge took up the running from early one and Walsh dictated affairs, first setting a slow pace before allowing Whatuthink to take it up on the final circuit.
Whatuthink set a steady gallop but Zaidpour was also on his shoulders and Walsh was quick to send his mount back into the lead after the third last.
Voler La Vedette came up to challenge but Zaidpour had two much in hand and it was the 11-8 shot who came home a length to the good.
"I didn't know whether to go slow in front or follow her," Walsh explained.
"I'd given her a lead the last twice and she swept past and I thought she might do the same again.
"It was clear at the start no-one was going to make it (the running), so I sauntered along in front.
"He just loves soft ground - you couldn't have it soft enough for him."
Chicago Grey finished third of the five runners.