Your description of a z-axis isn't quite right. I think you mean to say dual Y-axis. A z-axis would result in a three-dimensional rendering, compared to dual y-axis which is still two-dimensional but allows for different data sets to be rendered on the same graph with different y-axis scales.

SSRS 2005 doesn't support dual y-axis natively -- a third-party tool like Dundas supposedly can.

SSRS 2008 should be able to define dual y-axis, however. Although I have not had the need to create a dual-scaled graph, here are a couple of links on how to do it:

http://technet.microsoft.com/en-us/library/dd207018(v=sql.105).aspx

http://sqlbg.wordpress.com/2010/03/18/creating-dual-y-axis-chart-in-ssrs-2008/[/url]

BUT, before deciding to render your data using dual-scaled graphs, you might want to read the following short article by Stephen Few, a data visualization expert. His article highlights the problems of using this type graph:

http://www.perceptualedge.com/articles/visual_business_intelligence/dual-scaled_axes.pdf

--Pete