The tertiary axis is not a third orthogonal axis, and in general it's not
very effective in terms of understanding the data.
That can be said about 3D charts, as well: in general they are not very
effective in terms of presenting understandable data.
Excel has no native 3D x-y-z charts, and any renderings of 3D objects on a
2D medium (paper or computer screen) is going to be difficult to read
Jon Peltier, Microsoft Excel MVP
Tutorials and Custom Solutions
Peltier Technical Services, Inc. - http://PeltierTech.com