When Zac sets out to try to stop Dar from casting the final spell he carries his ax in his right hand and his bag is by his right hip. The ax is over his shoulder on page 66 when he first sets out. It is then held as a weapon on page 72.

On his return to the tree house Zac carries his ax in a relaxed manner in his left hand. His bag is by his left hip.

It's almost as though a mirror image is used.