If he was a witness to the murder, he had to be pretty close, looking from let's say a bedroom window. It was 10 pm, dark, and to recognize somebody with confidence, you would have to be fairly close. I wonder if Robert L Vonhafften knew the Robbins children. Another thing in our favour, is that at least Zodiac turned right on Cherry. In the Bus Bomb letter, he seemed very familiar with 'blocks', time and distance despite being in the park at times.
If we take the Bus Bomb letter wording as true, he entered via Spruce Street. He said after all in the Bus Bomb Letter that " I disappeared into the park a block + a half away never to be seen again." He then travels via the park to the wooded area near his residence, at the base of West Pacific Avenue. I have drawn a diagram below, where he not only is concealed in dense foliage, but it matches his wording in the Bus Bomb letter exactly. In this position he is approximately 150 feet from Presidio Boulevard; "there was only 2 groups of parking about 10 min apart, then the motor cicles went by about 150 ft away." Presidio Boulevard is not only 150 feet from this dense overgrowth, but Presidio Boulevard travels from south to north before turning north west, Zodiac stated " there was only 2 groups of parking about 10 min apart then the motor cicles went by about 150 ft away going from south to north west." Here is a diagram where Zodiac could have been observing from, allowing a quick exit from the park if need be.
Zodiac also stated "The dogs never came with in 2 blocks of me + they were to the west." From here the dogs would unlikely have reached this area so soon after the murder, they would have been to the west and certainly not within 2 blocks. Also had he observed motorcycles on Presidio Boulevard, he would also see the lights, firetrucks and sirens on Arguello Boulevard "there was only 2 groups of parking about 10 min apart." Ok it's not 10 mins, more like 3-4 minutes from one side of the park to the other by car, but certainly 10 minutes walking, which is what he was doing after all.
