I bought a heavily infected Zeiss lens without any coating. I put it under an UV lamp (made for killing algae in a garden pond for a few days. Funghi was gone afterwards - I could not even detect any marks or hints on the infection. I kept that lens aside of other lenses - but even a couple of month later it was clean inside. Do not know if this technique would work with modern multi-coated lenses. I would expect that maybe not enough UV radiation reaches the inner parts of the lens or that the funghi may leaves marks on the coating.