Using Global Mapper
The licensed Global Mapper Software allows to convert .laz files into .las/.ascii files.
For more information: http://www.globalmapper.com.
The LAStools software of rapidlasso GmbH contains a few open source tools such as "laszip" and "las2txt" that convert .laz files into .las/.ascii files.
In order to download LAStools and obtain more information: http://rapidlasso.com/LAStools.
Disclaimer: Pix4D publishes this information as a courtesy to its customers. Because this information may not be accurate, Pix4D makes no warranty of any kind, expressed or implied, with respect to its validity.