Whilst in New Zealand filming Maddigan's Quest, Zac's mother was contacted by the casting agent for Alex Rider for the movie Stormbreaker. Zac was auditioned from New Zealand via video at least twice.
Unfortunatly, the successful candidate needed to start pre-production training (such as learning to snow board, ride a quad etc.) in early June - it was not possible to get back in time as Zac was contracted to Maddigan's Quest until July. A huge pity as Zac did not need all the extra training - he had all those skills already.
Zac had to wear some contact lenses for his role as Little Casanova, as did the brown eyed David Tennant (they were both sent to the same optician) - these lenses were even more startling blue than those he wore in Wah Wah!
Zac wore blue contact lenses for his role in Wah Wah. The opening shots are of Zac's eyes coming over the front seats of a car - in some cinemas this can mean his eyes are projected up to 60 feet wide! Seeing as Zac's eyes are brown, it is amazing that he was auditioned at all!