i tried to install in cacko thru the add/remove and thru 'ipkg install' and it doesn't work.
IIRC ipk format is the same as a debian package. I am using the ipkg-build.sh script, I don't know anything about debian packages.
The ipk installs the library to /opt/Qtopia/lib and sets up the required links. It installs fine on my SL-C750 with original Sharp ROM and I tested it using a test program that comes with libz called "minigzip" so I know that it works.
Please can you be more specific than "it doesn't work". Were there any error messages and what were they ? Can you see the file /opt/Qtopia/lib/libz.so.1.2.5 after installing ?
I don't have Cacko but I would have thought that the path /opt/Qtopia exists... or does it not ?
Did you download the ipk properly ? Maybe there was an error. I just checked the file on the webserver, it looks OK to me. I downloaded myself to check and my browser un-gzipped it when it shouldn't have. I suspect this is what happened to you. Was your download 50 KB or 43 KB ?
I have added a MIME type to the server so it should download without decompressing now. Please try downloading it again.