First let me say that I wear my eyeglasses all of the time when I'm not doing photography.
I have the Zemlin eyecups on both my Z8 and Z9, and while they work ok with glasses, I don't like the pressure that I end up exerting on my eyeglasses when I try to look at the view finder with glasses on. So I actually prefer to go without eyeglasses and rely on the diopter correction to keep things sufficiently in focus.
I have at times worn my eyeglasses on retention straps, so that I could quickly put them on and off when needed, but I have found that became a bit of a hassle when I'm using a shoulder strap (which is nearly all of the time when I'm shooting wildlife). So now I typically just go without wearing my glasses at all, and just keep them in a case in my pocket so that I have them with me if needed.
If I am going to be walking for any length of time, then often I will go ahead and put my glasses on, but once I stop to shoot they always go back in my pocket. This is also the case when I'm doing landscape photography.
YMMV.