Doberman with nasal polyps-given Nizoral tablets 200mg. Will these help?  Any ideas very welcome.

Depends what the polyps are.  Polyp is just a description of a shape really.  If the cause is thought to be fungal that I suppose it will help.  Or perhaps the vet thought there was a concurrent fungal infection.  Why don't you ask the vet?

Vet seems to think Fungal.

steroids work in most people.  Is it on both sides? If it is on one side I would want a biopsy as that's what we do in humans.

On both sides. Once cleared will it recure ?

I don't know about in dogs but in people yes they can quite often recur although with some people after a course of steroids they can disappear and not come back for many years.