• tried this
    1) Open Terminal.
    2) Type “unzip” and a space, then drag/drop the zip file into the Terminal window.
    3) Press Enter and the zip file will be unzipped, storing all files on your computer.

    and also this

    Open and run "Terminal".

    Change the "Directory" to the Desktop (where you initially moved the Zip file to be unzipped). In the open "Terminal" interface, type in these commands:

    cd /desktop
    Unzip the Zip file by typing in this command; unzip {name of the Zip file}.zip.

    Now Terminal will reveal some lines of code to indicate that the Zip file has been successfully unzipped. Your files can now be accessed on your desktop.

    Neither of those worked, so have just downloaded unarchiver, which has done the trick (£30) for winzip felt a bit rich..

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