I wish I did know a good way to cool. My NM greenhouse gets to over 100 with all the vents and doors open.
If your water isn't too hard you could use a misting system that goes off 3 or 4 times a day during the summer. I tried that but our water turned the plants and walls white.
A long time ago I saw a greenhouse that had one end wall of cloth, and drippers from above kept the cloth wet and they used fans outside, blowing the air from the wet cloth into the greenhouse.
Probably your best idea is to have a shade area outside and keep your less hardy plants in the greenhouse all winter. My daughter has a greenhouse in Texas and her greenhouse was getting to 130 so she can't use it in summer at all.
