When a zip file is open you can access the search function from the context menu available in the file list view or from the folder tree.
The search function
In the File(s) to search edit zone enter the file name (c:\myfolder\file.txt) or file.txt (all file.txt entries in the archive file will be displayed), or use skeletons like (* and ? are allowed).
You can perform more than one search at a time, just leave a space between two definitions. You can also use ',' or ';' as delimiters
E.g. : *.jpg *.html or *.jpg,*.html or *.jpg;*..html
When a search result is displayed you can process a second search based on this result. Click the Search on result item.
A popup menu is available when the result is displayed.
The Back menu item return to the zip file.
