As usual, Quba can display UN/CEFACT CII and UBL .xml files as well as PDFs.
In version 1.0.0, hybrid invoices now open in a single tab with a button to visualize the embedded XML.
In terms of Factur-X/ZUGFeRD extended support for XML-encoded "Skonto" (cash discount) has been added.
Please report any Factur-X/ZUGFeRD samples where anything is wrong or missing.