the 1st real suspect was a park ranger at Yosemite. Other rangers contacted LE and this guy was questioned by the FBI.
He was a close resemblance to the zodiac composite, two separate rangers found him acting strangely and even stalking normal hikers . he was eliminated by handwriting , the report gave a name that is blotted out.... he was off the days of the attacks it said.
I watched the cold case files Zodiac episode in jan 2010, it had a mention of this , a year later that part of the show had been removed