Zak joined the club on 14th December 2022 as Paul Phillips’ first signing.

The Sheffield-born striker began his career with Manchester United and he made it to the first team’s subs bench in May 2017 for their final day Premier League game against Crystal Palace.

During the 2018-19 season, under Jose Mourinho, Dearnley trained with the club’s senior squad in the build-up to the Champions League tie with Juventus.

In January 2019 Dearnley was loaned to League Two side Oldham Athletic, making his professional debut on February 9th against Crawley Town and scoring Oldham’s second goal in a 3–0 victory.

His loan was terminated on April 30th due to injury after making nine appearances.  In June 2019 Dearnley left United following the expiration of his contract.

He joined North West Counties side New Mills but made just one appearance for the club before returning to Oldham Athletic in January 2020. He remained there until January 2022 when he had his contract terminated by mutual consent.

Dearnley then joined FC Halifax Town in the National League, subsequently moving on to Buxton prior to signing for Liversedge in September 2022, from where he joins Guiseley.

As a youngster Dearnley represented England Under-16s and England Under-18 Schools.

Dearnley joined New Mills on a dual registration deal on 27th January 2023 to regain match fitness after a spell out injured.

On 18th February 2023 it was confirmed that Dearnley had left the club to sign for Stocksbridge Park Steels.