are you 1 owner? do you know how they were used?
i would advise not to clean your lenses if it isn`t absolutely neccessary - there always is a risk the position of the glasses will be changed. before an attemp of cleaning consider if quality of dirty lenses is so poor that it`s better to risk a serious demage.
If you think the dust is causing poor image quality (insane amount indeed), send an email to Zeiss, they are extremely responsive (of course, it may be less expensive to buy a new lens than to ship the lens to Zeiss and have it serviced).