The Zodiac Killer may have chosen Donna Lass as a victim because it was an area he frequently/occasionally visited for business, or had spent some of his time vacationing at Lake Tahoe. As previously mentioned, the Pines postcard mailed on March 22nd 1971 may not have been the first time the Zodiac Killer targeted South Lake Tahoe, when for several weeks in November 1969, during the height of his "bombing campaign" in San Francisco, several telephoned threats to school bus routes in Lake Tahoe were issued to Reno authorities, including Incline Village which became the centerpiece of his Pines card over a year later. The Zodiac Killer used a Forest Pines at Incline Village advertisement from the newspapers to attach to his postcard on March 22nd 1971. So what are the options?

However, if the threats were from the Zodiac Killer himself, then branching his terror beyond the Bay Area to spread fear into the wider community (especially somewhere he was familiar with), appears to be something that would satisfy his ego. If these threatening calls to Lake Tahoe occurred in the weeks before the above published newspaper article, then the calls were likely placed between November 3rd 1969 and November 23rd 1969 (if few weeks was a maximum of three). The Zodiac Killer's "Bus Bomb" letter was mailed on November 9th 1969.
Is it possible that a hoaxer local to the Lake Tahoe area made the threatening calls to generate some "excitement" in the location they lived, which then featured in a Sacramento newspaper on November 24th 1969 and was stumbled across by Zodiac in March 1971, who decided to mail the Pines card with an Incline Village advertisement so as to capitalize on the threats to school buses from 16 months earlier? Is that a realistic scenario, bearing in mind that Donna Lass lived in San Francisco and worked at the Letterman General Hospital in Presidio Park (that Zodiac escaped into), before moving to South Lake Tahoe where she was abducted and murdered. The common thread being the Zodiac Killer.
Isn't it more likely that the Zodiac Killer made the school bus threats to Lake Tahoe in 1969 because he had some connection to that area, which is why the disappearance of Donna Lass just over nine months later, on September 6th 1970, triggered his interest? He may have decided to claim his involvement in her disappearance (and murder) to continue the theme of Lake Tahoe, and thereby bolster his earlier threats as genuine. If his connection to the Lake Tahoe area was a viable one in 1969, then it is not without merit that he could be responsible for the young 25-year-old nurse's murder, Especially if the Zodiac Killer was familiar with Donna Lass (either directly) or through her friend, Jo Anne Goettsche, whom she lived with at 4122 Balboa Street in San Francisco during the Paul Stine murder (10/11/69). Jo Anne Goettsche had moved to 225 Mallorca Way in the Marina District in 1970 - an area Zodiac appeared to be heading towards as he traveled through Presidio Park on October 11th 1969. Could the Zodiac Killer have known (or become aware) of Jo Anne Goettsche's plans to travel from San Francisco to South Lake Tahoe to visit Donna Lass late on the evening of September 6th 1970? The timing of her disappearance less than 24 hours earlier may be significant. It's extremely unlikely that the Zodiac Killer got wind of Jo Anne Goettsche's intentions, but stranger things have happened.
Officers in Lake Tahoe discounted the caller's claim that he was the Zodiac slayer, but I wonder what the same officers thought sixteen months later, on March 22nd 1971?
EXTRA READING: WALKING TOWARDS THE MARINA DISTRICT