Another error was discovered in the ell2utm function. The test for UTM zones less than zero should be a test for zones less than OR EQUAL TO zero. Replace
The error occurs only for zone 60 (longitudes 174 - <180 east).
Thanks to Mohammad Ali Goudarzi for pointing out the error. I will post a new version of the toolbox with this correction and the ones given in my 27 Jul 2013 comment as soon as possible.
03 Mar 2014
Toolbox for angle, coordinate and date conversions and transformations. Version 2.97.
Sorry I didn't see your post sooner. Here is an example of converting geocentric Cartesian coordinates to ellipsoidal with xyz2ell3 and then back again with ell2xyz:
As you can see, the differences are less than a micron.