Curious : seems freeCad is very slow to import iges files from ZSurf! 2 minutes ! ( for 3.38 Megas ! )
Moi it's 1 second!

Idem when the same file is saved from Moi in IGES! it was the simple Pilou text surface above!
It's the same for you?

http://moiscript.weebly.com/uploads/3/9/3/8/3938813/srf.igs