[Tex/LaTex] Cross referencing: zref-xr does not detect .aux file of second document

cross-referencingzref

So I am trying to crossreference labels across two documents: draft.tex and appendix.tex. When compiling I get the following error message:

./draft04.tex:16: Package zref-xr Warning: File `appendix.aux' not found or    empty,(zref-xr)                labels not imported on input line 16.

These are the two preamples of the documents including an example of a label and a reference.

First draft.tex: 

\documentclass[11pt]{article}

\usepackage{mla}
\usepackage{graphicx}
\usepackage{wrapfig}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{csquotes}
\usepackage[document]{ragged2e}
\usepackage[english]{babel}
\usepackage[backend=biber,style=mla]{biblatex}
\usepackage[hidelinks]{hyperref}
\usepackage{zref-xr,zref-user}
\zexternaldocument*{appendix}
\providecommand{\biburldatelong}{}
\bibliography{biblio.bib}

\begin{document}
...
see \ref{fig:01_examples}.
...
\end{document}

Then appendix.tex: 

\documentclass[11pt]{article}

\usepackage{mla_appendix}
\usepackage{graphicx}
\usepackage{wrapfig}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{csquotes}
\usepackage[document]{ragged2e}
\usepackage[english]{babel}
\usepackage[hidelinks]{hyperref}
\usepackage{zref-xr,zref-user}
\zexternaldocument*{draft04}
\providecommand{\biburldatelong}{}

\begin{document}
...
\listoffigures
\newpage

\begin{figure}
    \includegraphics[width=\textwidth]{img/01introduction/card_blackOps.jpg}
    \caption{Testing the crossreference}
    \label{fig:01_examples}
\end{figure}

...
\end{document}

These two documents are in the same directory. I really have no idea, why the appendix.aux is not found, since I can open it and it does contain this line, which I thought was needed for the crossreference: 

\newlabel{fig:01_examples}{{1}{2}{Testing the crossreference\relax }{figure.1}{}}

What am I doing wrong? Help would be very much appreciated.

Best Answer

I get

Package zref-xr Info: Label import from `appendix.aux' on input line 17.
Package zref-xr Info: Statistics for `appendix.aux':
(zref-xr)             1 LaTeX label(s) found.

By default the label fig:01_examples is imported as zref label and can be referenced by \zref{fig:01_examples} (with zref-user). If you want the traditional LaTeX references, you need:

\usepackage[...]{hyperref}
\usepackage{nameref}
\usepackage{zref-xr}
\zxrsetup{toltxlabel}
\zexternaldocument*{appendix}

Then \ref{fig:01_examples} or \zref{fig:01_examples} can be used.

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