They explain how their technique differs from searches in CODIS (Combined DNA Index System): "Our genetic genealogy service is somewhat like familial search, but it differs in three very important ways: (1) we only search public genetic genealogy databases, not government-owned criminal (STR profile) databases, such as CODIS; (2) because the DNA SNP profiles we generate contain vastly more information than traditional STR profiles, genetic relatedness can be detected at a far greater distance (see Snapshot Kinship Inference); and (3) because genetic genealogy matches can be cross-referenced by name with traditional genealogy sources, such as Ancestry.com, existing family trees can be used to expedite tree-building and case-solving. This technology and our innovative techniques combine to create a groundbreaking system for forensic human identification".
Single nucleotide polymorphisms (SNPs) are the most frequent sequence variations in the human genome, occurring approximately once every 100 to 300 bp. Apart from identical twins, each individual has a unique combination of nucleotides at these positions. Thus, a SNP profile provides a kind of fingerprint. .Joseph James DeAngelo was identified and arrested only because crime-scene DNA had been preserved. This allowed forensic scientists to compare it to genetic material using modern techniques that determine the sequence of hundreds of thousands of DNA variants, or single nucleotide polymorphisms (SNPs), across the genome. This is the same genotyping approach used in consumer genetics testing and many biomedical studies.
It was reported in the Sacramento Bee newspaper in May 2018 that Detective Poyser expected to see results on the envelopes arrive by the summer, with CeCe Moore stating in July 2018 that "a team is already working to identify the Zodiac Killer, who shot and stabbed five people to death in Northern California in 1968 and 1969". Therefore, it's safe to assume that the Zodiac envelopes were submitted (likely to Parabon NanoLabs) nearly two-and-a-half years ago. Despite this being a highly efficient and successful company who submit DNA SNP profiles with greater reach, there has been no news forthcoming in the intervening twenty-eight months, thereby leaving two reasonable conclusions of:  DNA has been secured from the Zodiac envelopes but has failed to produce a match using GEDmatch databases and Family Tree DNA (which analyzes autosomal DNA, Y-DNA, and mitochondrial DNA). Or  No viable DNA has been secured from any Zodiac envelopes.