Recently Jarett Kobek, in his book "How to Find Zodiac", has looked into the fanzine culture, in which enthusiasts of a particular cultural phenomenon (such as the literary or musical genre) share their passions through a shared interest magazine. Hence the suggestion of the Zodiac Killer's ability to source the limited 1952 Tim Holt comic book to reproduce in his October 27th 1970 communication. The term was coined in a 1940 science fiction fanzine by Russ Chauvenet and first popularized within science fiction fandom, before being adopted by other communities.
Stanton Arthur Coblentz, born in San Francisco, was a science fiction author and poet, whose first published books began with "The Sunken World" in 1928 and continued into the 1970s, that included "When the Birds Fly South" (1945) and "Hidden World" (1955). When the Birds Fly South is a fantasy novel, first published by "The Wings Press" in Mill Valley, Marin County in 1945 (later reprinted in 1951). The story features Dan Prescott, an American adventurer, who discovers the hidden valley of Sobul in a mountainous region of Afghanistan, inhabited by a strange race of winged people known as the "Ibandru". He falls in love with one of them, Yasma, and they marry in a scene of general celebration. When fall comes, however, the Ibandru abandon their valley to fly south with the birds for the winter. Stanton Coblentz also authored and released the book "Mountain of the Sleeping Maiden & Other Poems" on January 1st 1946 - a reference to Mount Tamalpais, which overlooks Bolinas Lagoon in Marin County.
Was there a possibility that the Zodiac Killer knew about the works of Stanton Coblentz and where he lived, using the cryptic pasted text of "Birds Fly South" and "Hidden", next to each other in the communication, when he mailed a horoscope page to the Sacramento Bee newspaper on December 10th 1969, entitled "Day-By-Day Forecast for Cancer"? This was the date Leona Roberts was abducted from the 749 Tormey Avenue residence in Rodeo, California. Her body was discovered eighteen days later on December 28th 1969 at Bolinas Lagoon in Marin County, a north-south Pacific flyway for birds migrating south for the winter. On December 11th 1969, another possible Zodiac letter arrived in San Francisco with the title "Day-By-Day Forecast for Leo", leading one to conclude it may have been a play on words, insinuating that it was a "Forecast for Leona Roberts", who wasn't killed for at least a week after her abduction.
It seems rather uncanny that Leona Roberts was abducted on the same day the "Forecast for Cancer" horoscope letter arived on December 10th 1969 with the pasted text of "Zodiac" and "Birds Fly South", to be then followed by the "Forecast for Leo" horoscope page, with her body being found eighteen days later at Bolinas Lagoon in Marin County where "Birds Fly South", which was prominent in the book title of a science fiction author, whose home and the publishing house for this book, was located in Marin County. If that wasn't enough, somebody calling themself "Zodiac" made a phone call to Peggy Trainer and threatened her life on January 4th 1970. She lived at 749 Tormey Avenue in Rodeo, where Leona Roberts was abducted from on December 10th 1969. The two horoscope letters had not been published in the newspapers by January 4th 1970, meaning the phone caller was not mimicking the author of the letters in December. This phone call arrived just seven days after Leona Roberts' body was found at Bolinas Lagoon..
Was the Zodiac Killer laying down cryptic clues in the two horoscope letters, partly using the works of a book author, with the intention of pointing us towards the abduction and murder of Leona Roberts? The pseudonym of "Zodiac" being present in a communication the day of Leona Roberts abduction, and spoken in a phone call on January 4th 1970 to the address she was abducted from. If these were different individuals, then that is a coincidence worthy of science fiction and the writings of Stanton Arthur Coblentz.