@Johnny. Don't Worry, I don't. But Grevy-Zebras , for example, do not live in open plains and I've often seen them in other zoos standing and resting in the shade under trees at hot summer days, also I've seen Mountain Zebras enjoying resting in shade, so I think, shade is an neccessary for them, and there is no reason in the Tierpark, to give not shade places. i've seen some desert animals, which prefere shade places for sun places.
I've seen all the african equids in the Tierpark a few years ago at a very hot summer day, they were standing as close to the stable as they could, to get just a tiny point of shade....
And I have pictures of Mountain Zebras in the Desert, resting under a Tree, there are trees in deserts and open plains also....So if you would give them a protected tree in their enclosures, the zebras at the Tierpark would be very thankful for that.