If you used a Mac back in the 90's, then you remember that among Mac users, nobody ever used ZIP format for compressing files.  Everybody used SIT files instead and some used HQX, BIN or CPT files, but not a single Mac user zipped their files.  The reason is simple: ZIP files are not compatible with Mac resource forks (old Mac files before Mac OS X) and zipping an old Mac file (such as a Mac OS 9 application program) would destroy it, effectively stripping its resource fork.  That being said, zipping old Mac files under Mac OS X changed this.

When you zip files under Mac OS X, the files are split in two folders: The resource forks are binary encoded and split away, stored in a "__MACOSX" folder and the DATA forks are stored as is in its own folder.  In other words, if you inspect inside an OSX zipped file, you will see a "__MACOSX" folder and another folder named like what you zipped, but Mac OS X hides this "__MACOSX" folder from the typical user, so you can only see this with other OS'es such as Windows, Linux or Mac OS 9.  The "__MACOSX" folder contains the resource forks of all the files, binary encoded because that's the only way they can be stored in a ZIP file along with the DATA.  The file names inside the "__MACOSX" folder all begin with a dot.  All Mac files from versions BEFORE Mac OS X depend on those resource forks to even be useable.  Without their resource fork, Mac OS 1.x to 9.x application programs and most documents would be nothing.  Nada.  So you need both forks (resource and DATA) for old Mac files to work.

The problem is:

When you expand an OSX ZIP file under Mac OS 9, you will expectedly see both folders: One named "__MACOSX" as well as another folder containing all the files inside the ZIP... but every file icon will be blank/white.  Moreover, you will notice, sadly, that no file is useable at all. This is because no Mac OS 9 decompression utility knows how to join the two forks back together.  It's an OSX only thing.  OK, but now what?

Well, the solution is:

1) You need a Mac OS X computer, boot it and copy your ZIP file onto its desktop.

2) Expand the ZIP file under that Mac OS X computer with any ZIP tool, such as the one that comes with OSX or you can also use The Unarchiver.

3) Once your ZIP is expanded, OSX will instantly rebuild/join the resource forks and DATA forks and render your old Mac files useable.

4a) Now, you can use Stuffit or a similar app to produce a .sit (not .zip!) archive that you will be able to transfer on the old Mac and expand it there.

4b) ...OR you can create an hybrid HFS+ ISO disk image containing all those files, transfer it over to the old Mac and mount it there.  Launch Disk Utility and in the menu bar at the top choose: FILE > NEW > "Disk image from folder..." > Choose your expanded ZIP folder containing all your files.  Then when it asks you where to save the disk image, make sure you choose the image format at the bottom: "Hybrid image (HFS+/ISO/UDF)".

4c) ...OR you can create a HFS+ disk image, mount it (double-click it), copy all the expanded files on there, transfer it over to the old Mac and mount it there.  The Terminal command line follows.  Make sure you adapt "/Users/ben/Desktop/" to your OSX desktop path and "1M" to the amount of disk space big enough to store all your expanded files (you can see how much space they take by getting info in the Finder on the expanded ZIP folder) and you can go with gigabytes too (e.g. "2G" for 2 gigabytes) : hdiutil create -fs HFS+ -o "/Users/ben/Desktop/diskimage.dsk" -size 1M -layout SPUD -type UDIF -nospotlight