Like her mother, she shares a love of horses and the royal women will sometimes attend the races together.
When they are seen together, Bruce Durham, body language expert at BelievingBruce, commented on their relationship.
The expert explained why Princess Anne may appear uncomfortable during some outings.
“In one photo, we have discomfort showing from Princess Anne. She has her arms crossed, called ventral protecting,” Bruce said.
“It may be that what she is carrying simply feels more comfortable to be carried like this.
“But when compared to the open unprotected nature of Zara exposing her torso area, called ventral fronting, Zara most definitely looks the more comfortable of the two.”
Any signs of discomfort could have been caused by different interests between the royals, Bruce continued.
He added: “It also shows an example of Zara engaging with Princess Anne, but here, Princess Anne is looking away into the distance not at Zara.
He commented: “The outing shows both subjects mirroring each other.
“You can tell from the rise is Zara’s cheek and the look that is clearly visible on Princess Anne that this is an engaging conversation for both.
“You also have a mirrored head tilt as well as their torsos almost turned to each other at an identical angle.
“This indicates extreme comfort and joy in being in each other’s company at that moment.”