When you extract .zip file and .z file in aix and you get the error:

unzip archive.zip Archive: archive.zip End-of-central-directory signature not found. 

First try to check if the file is a valid zipfile with:

file archive.zip

Or you can try to use the od tool:

od -x archive.zip|more 

Solution 1: check filename

Remeber that the filename must end in an extension with a cap-Z, i.e. sample.file.Z. If your file does not, rename it and try the uncompress. Other tools will required different filenames:

• uncompress needs a file called sample.file.Z
• gunzip needs a file called sample.file.gz
• unzip needs a file called sample.file.zip

Solution 2: Using unzip

Download the unzip tool and try to use the downloaded tool.