Able Archer.!
Ok, access it, how... you mean the mod files itself to edit files in it... or are you instead, meaning... just how the heck do you get the mod unzipped, so that you can set the whole shooting match of the mod set up, so as to be able to play it...???
If it is indeed, the latter choice... then try using 7zip
The other possibility, is... you could have gotten a bum steer download... rare, but... that can & does occur, from time to time.
Only recourse then, to do... is to redownload the mod set & then retry unzipping it.
Now... if your intent is to edit them... is a wholle lot of things one needs to know & understand there... as anything left out, mis imput in... space added into the coding... too many things to name them all here... & yeah... crash & burnville here you come.
Beyond that small input there... not going to go further, suffice it to say, gotta be careful what tampering about in the files you do or else it all goes pear shaped.. big end up pear shaped...
https://i.makeagif.com/media/5-01-2016/B0RxAC.gif
M. M.