1995 Ford Contour no compression on all cylinders (no start

Hi, I'm an automotive student at Gaston college working on my associates degree, and recently my mothers car broke down while driving down the highway and would not start back up. After having it towed to the schools garage, and many test I discovered that the problem was a blown head gasket by use of a CDL test. After sending the head to a professional machine shop to have it machined and checked out and buying all the necessary gaskets, etc. For the proper repair and instlation. I installed everything using the proper instalation procdure & specs provided by the manufacturer, which I have done properly and succesfully many times in the past on numerous different makes and models. So when I completed everything and attempted to start the car, it would not start although it will turn over. I then double checked the timing, hoping it would be that simple without any such luck (still no start). I then did a compression test on all four cylinders and got a reading of 0 on all cylinders. SO, MY QUESTION TO YOU IS; WHAT SORT OF THINGS COULD CAUSE THIS TYPE PROBLEM? Thanks for your time and I'll be looking forward to your reply!