The way to add files to Application Library is to use "Add Files" option in ZINC Builder.
On Windows browse dialog does allow multiple selection of files to be added at ones but importing more then 9 files at once fails with runtime error.

To repeat issue:
#1
download attached archive
#2
unarchive and open .zinc project file
#3
switch to "Files" section to add files to application library
#4
try to select more then 9 files at once (dialog allows multiple selection) and choose "Open" in dialog to include files into library

Actual results:
- the error is shown with exact message that could vary between OS. For example it could be "Error: file selected outside of project directory (C:\Users\{USER}\{SOME_PATH})"
Expected results:
- files are added into library