Following a successful time in young riders, which culminated in victory in the Under 25 Championship at Bramham and an individual silver medal in the European Young Rider Championships in 2002, Zara made a dream start to her career at senior level in 2003 by finishing second at Burghley with Toytown.  A stylish display in the dressage arena and a fast clear across the country left her the surprise leader going in to the final show jumping and although one fence down dropped her to second behind the eventual Rolex Grand Slam champion Pippa Funnell, it was a performance that hinted at things to come.

Zara was subsequently long listed for the Athens Olympics in 2004 but her hopes were dashed by an injury to Toytown that ruled him out for the rest of the year.   She bounced back in 2005 with a great performance at Luhmuhlen CCI4* in Germany on Toytown where she finished on her dressage score to take second place. This earned her a place as an individual on the British team for the European Championships at Blenheim in September.   When Pippa Funnell’s ride, Primmore's Pride, had to be withdrawn, Zara was promoted onto the team. She rode into the history books by taking two gold medals on this, her senior debut, exceeding the achievement of her mother, HRH The Princess Royal, who won the individual title at the European Championships in 1971.

Zara and Toytown went on to win individual gold and team silver the following year at the World Equestrian Games in Aachen, Germany – Zara's first four-star Championship. This feat also earned Zara the BBC Sports Personality of the Year accolade.

Following Toytown’s retirement in 2009, Zara partnered several other horses at four-star level including Ardfield Magic Star and Glenbuck. But it was with High Kingdom, with whom she finished tenth at Burghley in 2011, that the Royal reclaimed her place on the senior team. She was part of the silver medal winning team in London 2012 and went on to finish second at Luhmuhlen CCI4* in 2013, just weeks before her pregnancy was announced.

In 2014 Zara was a member of the silver medal winning team at the World Equestrian Games in Normandy the only team member to jump clear both across the country and in the show jumping phase of the competition. More recently in 2017 at Lexington, Kentucky CCI4* Zara finished third on High Kingdom. 

In 2018 Zara welcomed daughter Lena to their family but only two months after giving birth Zara was back in the saddle competing, winning the old advanced at Wellington. In 2019 Zara is aiming for Bramham and Luhmühlen.