We have a couple of these too (two sizes). They are great for road trips and we used them a lot when they were babies and after their surgery. My little escape artist, Ivan, figured out how to get his paw in the zipper and open the door. We have to close off the zippers with twist ties now. He hasn't figured out how to untwist them...yet.
We also had a pop-up crate for travel that was made of the same material. He chewed through the mesh in that so we don't leave them alone for long in the pens in case he decided to try that again.