Although a Z-matrix is a relatively straightforward construct, it is often times difficult to find an appropriate definition. With increasing molecular size, there is a factorial increase in the number of Z-matrices possible, with only a few being actually intuitive and easy to handle for chemical studies. In addition, structural changes along a reaction may lead to an ill-defined (back-)transformation (from) to this coordinate system. An illustrative example of the problems faced is included in the Supporting Information.