As with any kind of car finance deal, applicants must be over 18 to secure a 0% APR agreement, despite the legal driving age being 17. This is because only adults can enter legally binding financial agreements of this kind.
That said, even being 18 doesn't guarantee approval for a 0% car finance deal. Lenders want to feel confident that you'll make the repayments, and a healthy credit history is the most important indicator of this. Good credit scores take time to build up, so you likely won't get accepted for a 0% car finance deal until you're at least a few years older.