I just watched your mirror-image video about the initials DH – whilst that is a possibility, I am more interested in the magazine you show in the final minute of the video (Detective Story) where the killer calls in with ‘This is Z speaking….’ . Was this your own discovery? It’s quite a find.
The mirror-image idea could be useful too – obviously plenty of people have tried that on the 340, I’m not sure if anyone has found good results trying that on the prose letters/drawings at all. I shall watch the remaining videos with interest.

Sorry for the late reply, I’m about 3 weeks in on researching ZK and these are my own ideas. I’m all about patterns and I watch everyones videos and papers on the Zodiac and deduce the knowledge. That Zodiac calling pic is on google search under Zodiac Killer Collage – I got good success with his overlays. Watch my new video on the 340 Cipher and the My name is Overlay. https://youtu.be/9iRn2IElIZw

Are we seriously back to accusing Donald Harden of being the Zodiac? Ugh. Stuff like this is why this case will never be solved.

I don’t know who he is yet.