Well, Dolphin-sans-Krusader, if you try to copy a file into an opened zip, overwrites the whole zip, but gives you a dialog to say you don’t want to do that. This is a reasonable flaw for beta software, I would say. Konqueror-sans-Krusader does the most reasonable thing, which is to detect that you are trying to modify an archive, and tell you that Konqueror can’t join you in your pursuit. Unfortunately, it also refers to the zip file as a ‘tar’ file, but that’s the breaks. This is with KDE 3.5.7.
Incidentally, I noticed that beta 2 of KDE 4 is released. I hope it stays possible to use fluxbox and ROX Filer with it as window manager and desktop, respectively. Especially the former. Already I had to devise some extremely clever workarounds to make this work without having to start up the KDE window manager and desktop first and then kill them.