zack azck zcak czak aczk cazk zakc azkc zkac kzac akzc kazc zcka czka zkca kzca ckza kcza ackz cakz akcz kacz ckaz kcaz
Note: these 'words' (valid or invalid) are all the permutations of the word zack. These words are obtained by scrambling the letters in zack.