AZdecrypt is a fast multi-threaded homophonic substitution cipher solver with a Windows GUI. AZdecrypt was used by an international three-person team of codebreakers who made a breakthrough with the Zodiac Killer's unsolved 340-character cipher on December 3rd, 2020, and announced one week later.

AZdecrypt might be flagged by most security software.

The decrypted code reads:

I HOPE YOU ARE HAVING LOTS OF FUN IN TRYING TO CATCH ME
THAT WASNT ME ON THE TV SHOW
WHICH BRINGS UP A POINT ABOUT ME
I AM NOT AFRAID OF THE GAS CHAMBER
BECAUSE IT WILL SEND ME TO PARADICE ALL THE SOONER
BECAUSE I NOW HAVE ENOUGH SLAVES TO WORK FOR ME
WHERE EVERYONE ELSE HAS NOTHING WHEN THEY REACH PARADICE
SO THEY ARE AFRAID OF DEATH
I AM NOT AFRAID BECAUSE I KNOW THAT MY NEW LIFE IS
LIFE WILL BE AN EASY ONE IN PARADICE DEATH

The members of the team that cracked the code are:

* Sam Blake (Australia)
* Jarl Van Eycke (Belgium)
* David Oranchak (USA)

You can read about cracking the cipher here.

Check out this video to see how they decrypted the code after 51 years.