Hi Stefan,
There are some 300-500mm diamond blades available that you could try, usually at reduced rotational speed compared to their smaller brothers. With glass (or similar) I suppose you want a continuous blade that may be difficult to find above 300mm diameter ( I found 1 at 300mm), but there are plenty of segmented blades (better material clearance for aggressive cutting) that are available in the 300 to 500mm diameter range. I suppose it goes without saying to be careful since you only have 1 piece of the Zerodur and these types of blades may induce some micro vibration which may not be good. On the other hand it may be just what you need. On problem is that as the size goes up so does the thickness of the blade (an hence heat generated).
Anyway here are a host of possible options. There is even a 300mm Husqvarna continuous edge diamond wheel listed in amongst the many at this link (also a 350mm EHWA with tiny gaps) ....
https://sydneytools.com.au/search?p=5&q=Diamond%20Blade
300mm Husqvarna continuous edge diamond wheel
https://sydneytools.com.au/product/h...-diamond-blade
350mm EHWA with tiny gaps
https://sydneytools.com.au/product/e...-diamond-blade
PFERD is a quality manufacturer I would check with them (1300 073373) about using their large diamaeter segmented wheels to
carefully cut glass. (I'm fairly sure they'll say not to), but .... here's an example of a 350mm wheel for info....
https://www.pferd.com.au/diamond-cut...se-segmented-t
Best
JA