conflict tkz-euclide and nag?

Question

Am I doing something wrong and is this meant to happen?

%\documentclass{minimal} edit: should not be used
\documentclass{article}
\usepackage{tkz-euclide}
\usetkzobj{all}
\RequirePackage[l2tabu,orthodox]{nag}
\begin{document}
  \begin{center}
  \begin{tikzpicture}
     \tkzInit[xmin=-9, xmax=6, ymin=-0.7, ymax=5]
     \tkzDefPoint(0,0){x}
     \tkzDrawPoints(x)
     \tkzLabelPoints[below](x)
  \end{tikzpicture}
  \end{center}
\end{document}

If I try to compile this (with pdflatex or xelatex) I get the following error

! Incomplete \iffalse; all text was ignored after line xx.
<inserted text> 
                \fi

If I leave off the \begin{center} and corresponding \end{center} the error message changes to:

Runaway argument?
\@xa \looseends \@xa :\@xa =\nag@envstack \do {\@xa \ifx \looseends \relax \ETC.
! File ended while scanning use of \@tfor.
<inserted text> 
                \par

1. Could someone explain this error message to me.
2. If I comment out either \RequirePackage[..]{nag} or \tkzInit[..] the error vanishes.

Answer 1

There is a name conflict between nag.sty and tkz-tools-base.tex (which is input via tkz-euclide.sty).

From nag.sty:

\let\@xa\expandafter

From tkz-tools-base.tex:

\global\let\@xa\tkz@init@xmin

Without one (or both) of the two package authors resolving the conflict by renaming things, I don't think you use the two packages together.