As I understand it the Block option comes from a file having low integrity level (usual when dowloading from internet). It's part of the file permission system since Vista I think.
There are various utilities to modify those permissions, in your case the best bet is probably CHML, a little command-line app : chml: a tool to control Windows Integrity Levels
You can use it manually in a command prompt or make a .bat file to automatize, something like this should work :
This first line changes the current drive to D then the current working directory to \PDF, modify these lines as you see fit.
for /r %%f in (*.*) do chml "%%f" -rl -b
The last line removes integrity levels from all files in the folder (D:\PDF) and all its subfolders recursively (/r).
Copy the text in notepad then save as something.bat. Click on it to execute.
Note : I never noticed your problem when decompressing via 7-zip (7-Zip), maybe using that instead of the built-in windows zip might solve your problem...