To cite zoom in publications use:

Barbu, CM. (2013). zoom: A spatial data visualization tool (Version 2.0.4). Available from https://github.com/cbarbu/R-package-zoom

Corresponding BibTeX entry:

  @Manual{,
    title = {zoom: A spatial data visualization tool},
    author = {Corentin M Barbu},
    year = {2013},
    note = {(Version 2.0.4)},
    url = {https://github.com/cbarbu/R-package-zoom},
  }