We made some changes before re-printing the wedge enclosed by the surfaces \(x=0, z=0, z=1-y\), and \(x=y^2\). I altered the PlotPoints in the Mathematica code from 100 to 400, which made the curve of intersection between the \(x=y^2\) and \(y+z=1\) surfaces smoother on Cinema 4D.  I also made each side about 8 cm long instead of 7 cm and I made the equations larger.

The result was that the top vertex still looks messy and the  “\(z\)” on the bottom face of the object is not clear, but that can be fixed with a razorblade (see image below). Changing the PlotPoints in the Mathematica code made the curve much smoother and the equations look nicer. You can find this object on Thingiverse here.