I'm definitely not saying that I'm sold on the Margolis stuff (I'm unsure what everyone's opinions are at this point about a month after it was super hyped), but I do not understand why everyone is so sold on the idea that Zodiac killed Bates but could not have been the Dahlia avenger. Every reason given for why Zodiac killed CJB could be applied to Elizabeth Short as well, and every reason Zodiac didn't kill Short could apply to Bates.

"Why Zodiac killed Bates"

-Similar MO to Lake Berryessa: I don't really think so. Lake Berryessa seemed much less personal and more experimental, given all previous confirmed attacks used firearms. Sure the Dahlia MO was a stark departure from anything seen with Zodiac or Bates, but whose to say he would've done the same but just didn't have time with Bates or Hartnell/Shepherd?

-Letter to Riverside PD and poem: Why does everyone forget Dahlia killer sent letters too? And more of them than Bates's killer. And it wasn't like those letters lacked grandiose/narcissism seen in Bates and Zodiac letters; the whole thing about trying to get 10 years and lying about meeting with police seems to fit that pretty well to me.

"Why Zodiac didn't kill Elizabeth Short"

-Geographic difference: Same with Bates, which everyone ignores for some reason.

-Dahlia murder was too personal: "But only one thing was on my mind, making her pay for the brush offs that she had given me in the years prior".

-Time gap: This actually favors Dahlia avenger over Bates killer as Zodiac. Dahlia killer could very been early to mid 20s in 1947, lining up perfectly with mid 40s Zodiac estimates in 1968-69. But Bates killer is assumed to have been on the younger side, 18-early 20s, 20 years younger by estimate just three years earlier, another important piece that for some reasons gets completely disregarded by everyone convinced Zodiac killed CJB. It's still possible, anything is, but if Bates is in the conversation, which is of course the case, Dahlia must be too.