As this package is now released via CTAN, it's hightly recommended to use the TeX Live Manager for installation.
Additionally for it's possible to use the Island of TeX's DEPP project to create a minimal portable TeX Live installation only including the dependencies for this kind of documents. This repository includes a DEPENDS.txt for this purpose.
Please be aware that the soft dependencies are those required to typeset the demo file.
This package is not yet released to CTAN, but it provides an \pkg{l3build} installation script and demo files. Details on usage can be found in the l3build documentation/0).
To get started one can run
l3build doc
within the repositories root directory.
This will build the Demo project as well as the current status of the documentation within the subdirectory build/doc.
To Install the package within you $TEXMFHOME there is also the install action
l3build install
This will install the zugferd.sty as well as the zugferd-invoice.sty and afterwards the TeX compiler will be able to find and use them.