The Monticello communication was insinuating the murder of Kathy Bilek (18), who died in the Villa Montalvo woods on April 11th 1971, by using the burial site of her namesake Kathy Snoozy (15), who was murdered alongside her friend Debra Furlong (14) in San Jose on August 3rd 1969. Three despicable crimes, claimed by the Zodiac Killer in communications on November 8th 1969, May 1971 and July 13th 1971. However, unlike the Pines postcard, all the wording pasted on the Monticello communication was inspired by the newspaper articles about the three murder victims, Snoozy, Furlong and Bilek.
The Zodiac Killer pasted the following message into the correspondence: "Near Monticello Shought Victims 21 ... In The Woods Dies April". The wording was totally relevant to the killing of the three young girls, such as "near Monticello", "sought", "victims", "in the woods" and "April". Due to errors in the 1998 DNA chart, I am unsure whether the Zodiac Killer deliberately misspelled "sought", or it was typed incorrectly in the chart.
Many newspaper articles headlined with "near Saratoga" and "near Montalvo" to describe where Kathy Bilek was killed, so it's easy to see how the Zodiac Killer derived the clue "near Monticello" in his July 13th 1971 communication. Kathy Bilek was described as being found "in woods" or "in the woods", making this connection even easier. Countless newspaper articles mentioned that a link was being "sought" between the murder of Kathy Bilek and the double slaying of Snoozy & Furlong, all stabbed dozens of times in similar fashion. Not to mention that a vicious killer was being "sought" in both the Saratoga and San Jose attacks (altered to "shought" for whatever reason). Strangely, the Zodiac Killer pasted "victims 21" rather than "victim 21", despite "victim" being widely available. But when you look at the numerous articles postulating a link between all three victims, it's easy to understand why the Zodiac Killer chose "victims", to suggest his involvement in all three murders, within his total. The pasted "April" cutting easily sourced and inspired by the date of the newspaper in 1971. The Zodiac Killer pasted a message on July 13th 1971 comprised of language taken from newspaper articles, about victims he was claiming in his running total - building upon the Pines postcard in a much more creative way.