There are three noticeable elements on the 340 cipher - the unusual opening of HER (contained in CIPHER), the reversed K on the sixth row and the "near Zodiac" on the final line. However, their positioning is problematic regarding a Zodiac introduction and incorporating "cipher" into the 340 cryptogram. But not if we vertically flip the cipher on Dave Oranchak's Webtoy. The Zodiac Killer deliberately reversed or flipped the K on the 340 cipher, he deliberately flipped the text on the October 5th 1970 card with "Fk I'm crackproof", and did a similar thing with the "N" on the October 27th 1970 communication, that incorporated "sorry no cipher". The Halloween card also has Paradice and Slaves that can be found in the 340 cipher. So, with no further ado, let us flip the 340 cipher and place the entire introductory text from the April 20th 1970 letter into the 340 cipher.
We just need to change two words from past to present tense. If the solution to the 13 Symbol cipher was "Fk I'm crackproof" as previously shown here, then I would expect this to be the answer on the bottom line of the 340 cipher as well. Both ciphers being the same response to Dr. Marsh. Here is the introduction to the April 20th 1970 letter "This is the Zodiac speaking. By the way have you cracked the last cipher I sent you? My name is__ Fk, I'm crackproof". Here is the new format "This is the Zodiac speaking. Can you crack the cipher. My name is__ Fk I'm crackproof". Now let's introduce this into the flipped 340 cipher. It must accommodate the "HER" of "CIPHER", accommodate the "near Zodiac", accommodate "Fk I'm crackproof" and accommodate the dash symbol after "My name is".