If there is at least one file from a password protected Zip archive available unencrypted, Known Plaintext attack instantly decrypts the whole archive for you, regardless of the password length.
Select Known Plaintext tab from Settings Dialog Box to control the following options:
Plaintext file location
Plaintext file should be zipped without encryption file byte-by-byte equal to the one you have among others in the encrypted zip archive.
Use Key
If Known Plaintext attack has been performed previously and encryption key for this archive has been already found you can use it to decrypt the file.