Just a quick recap: The author of the 38 character code prominently featured two sections of the 340 cipher, that included the beginning 4 ciphertext characters of the 340 cipher, and the last 5 ciphertext characters of the 340 cipher. The only logical reason for the Zodiac Killer to have done this, would have been to give us a clue to the solving of the 340 cipher. When the code key is applied to the 340 cipher before any period 19 (diagonal shift), the first 4 plaintext characters of the 340 cipher spell IRON. The last 5 plaintext characters spell DEATH. As previously pointed out, a hoaxer would have had to be extremely lucky to keep the beginning and ending of the 340 cipher intact, to the tune of 4 & 5 characters (when creating the Z38), that just happened to create two English words in these notable positions. One would have expected a lazy hoaxer to replicate ciphertext characters 333 to 338 in the 340 cipher, because these characters were close to the spelling of "Zodiac". But the author of the December 7th 1969 letter refrained from doing this, choosing to separate these 6 ciphertext characters, so as to form the word DEATH at the end of the 38 character code. See here.
The red rectangle above (around the first three rows of the Z38 code) represents the first 18 rows of the Z340 cipher, These sections both begin with the letter H and end with the number 9 (or reversed P), The last line in the red rectangle contains five characters, all of which can be found on the last line of the 340 cipher (that is solved only using the period 19 diagonal shift). If you apply the period 19 shift to the red rectangle of the Z38, you get H+, mirroring the first two characters seen when you apply the period 19 shift to the 340 ciphertext. The blue rectangle (around the last two rows of the Z38 code) represents the last two rows of the Z340 (solved absent of the period 19 diagonal shift). The final five characters in the blue rectangle spell DEATH when using the 340 code key. The author of the December 7th 1969 letter (containing the Z38 code) also predated the appeal to Melvin Belli by stating "I just need help". The Zodiac Killer could not have copied the December 7th letter because it was unpublished by the time the Melvin Belli letter was mailed on December 20th 1969. It is such a shame that the majority of the Zodiac community dismiss this communication (and its sister communication on December 16th 1969) based on their extensive research of "it doesn't look like a Zodiac letter". A great opportunity to reveal another Zodiac message is sadly being ignored.
For black and white issue..