In case this wasn't obvious, the issue isn't cleaning methods. It's Zeiss will try to find a way out of their responsibility and so are not worth the cost for users who rely on warranties. If you are stretching your budget beyond what you can afford without missing it, Zeiss is a poor bet.
I've used Dawn on every lens I've ever had. No problem. It wasn't the problem with that Zeiss scope either. They just seized on that point to avoid covering a manufacturing defect.
I just remembered I have a pair of Zeiss lenses in eyeglasses that are several years old. Still good.
