Which software you are using for zipping them?
For compression level,select "store" (there will be other levels like best,good,fast etc). I use 7z and I select "store"
Or fine ,let's go by better road.
Step 1:- open construct 3
Step 2.:- create a "new project" and download it in form of .c3p
Step 3:- open that .c3p using your compressing software. To do this, right click on it and select "open archive". REMEMBER, I am saying open,not extract
Step 4:- add any small random file (like any small text file). To do this, drag the file into the compression window. It will get added
Step 5:- Then select all files (excluding that file you just added ) and delete them.
Why I said to add a random file:- if you will not add it then in this step, your .c3p file will get delete
Step 6:- open your project folder. You will see many things like event folder,fonts folder media folder etc. Select all and drag into the compressing software's window. All files will get added into our .c3p file
Step 7:- now you can delete that 'random' file which you added. It is now not needed.
Step 8 :- close the compressing software's window. It will give an alert :- the contenta of the archive has changed. Do you want that? (" Something like that") . Select yes
Step 9:- hurray, now test your file in construct 3
If this also doesn't works then don't worry. Your problem is very,very easy. Just relax