Think harder. If the medicines require a signed doctor's prescription, then they are by definition restricted. At least in the country in which they were prescribed and therefore quite possibly in AU and NZ. While the fact you have a signed Rx from another country might help you meet the restriction, it has really has no bearing on the question as to whether the medicine is subject to restrictions in AU.

There are also other medicines which might be available over the counter in your country that are restricted in AU.

It's pretty simple. The question asks you to declare, "Goods that *may* be prohibited or subject to restrictions, *such as medicines*".

So think again. There is no penalty for ticking Yes and then asking the customs officer about your items. But there can be serious trouble if you tick no and then items are found.