Rachael Ngeungeu Te Irirangi Beamish was born at Waiariki, Mercer, Waikato, on 10 October 1893, the third of ten children of Richard Evanson Beamish, a settler and later master mariner, and his wife, Rangi Takotokino Emere (Emily) Maxwell. Rangi was the daughter of Ānaru Mākiwhara (Andrew Maxwell) of Ngāi Tai and Ngāti Paoa, the last tohunga-tā-moko (tattoo expert) from Waikato, and his wife, Ngāpāoa Peti Herewini of Ngāti Naho, Ngāti Hourua, Ngāti Mahuta, Ngāti Hinetū and Ngāti Paoa. Rachael spent the first years of her life being raised by her grandparents, Ānaru and Peti. She grew up with Te Puea Hērangi, the future Kīngitanga leader, and her brothers and sisters. At the age of seven she returned to her parents and began attending Mercer School. Afterwards she entered a finishing school for young ladies in Queen Street, Auckland.
A fluent speaker in Māori and English, in 1917 Rachael began her long working career in the offices of her father’s relatives, Mason, Struthers and Company, specialists in dairy machinery, in Custom Street East, Auckland. Later that year she shifted to Whakatāne to handle Native Land Court work for a law firm. In 1920 Rachael began Māori land work for the Public Trust Office in Wellington, and in 1923 she joined the legal branch of the Native Department. During these years she was also pressed to stand for Parliament in the Western Māori electoral district, but declined. In 1926 she developed tuberculosis following severe influenza and spent some time in the Ōtaki Sanatorium and Hospital. A year later she was appointed Māori agent at the Native Land Court in Hamilton and Auckland and Te Puea’s social secretary, positions she held until 1938.
That year, on 13 August at Auckland, she married William Louis Zister, a farmer from Cargill, Ontario, Canada. Formerly a university student and then a trainee for priesthood, he had spent his working holidays on Nathaniel Beamish’s farm at Pukekawa. The Second World War soon intervened, but after William returned from serving overseas with the New Zealand Army, the couple settled on Rachael’s ancestral lands at Umupuia, Waiariki and Pukekawa. Here William bred and farmed Galloway cattle for beef, owned a rural delivery business for the Clevedon area, ran a cream pick-up, and made apple cider. There were no children of the marriage.
Rachael served on the Tainui Māori Trust Board from 1948 until at least 1968, representing Ngāi Tai, Ngāti Tamaoho and Te Koheriki of the Tāmaki–Wairoa district. She was an early member of the Māori Women’s Welfare League and in 1952 represented its patron, Te Puea Hērangi, at the second dominion conference. In 1951 she was appointed a justice of the peace. In 1950 she and William helped to establish a Catholic church at Clevedon, and from 1963 to 1965 Rachael worked with Te Rarawa leader Whina Cooper to raise funds to establish Te Ūnga Waka, the Auckland Catholic marae. She was appointed to the Hauraki Gulf Maritime Park Board in 1970.
In 1982 Rachael Zister gave a portion of her land at Umupuia to be set aside as a marae for her Ngāi Tai people. She raised money by opening her paddocks to campers and running a beachfront shop. She also set up the marae committee and trust, which raised funds and organised the building of a meeting house. Zister believed that this should be a place for her people to learn their history, but that both Pākehā and Māori should come. The dedication and celebration of the marae took place in November 1990. The governor general, Sir Paul Reeves, conducted the ceremony. This was a special day for Rachael and her family, who were able to witness the fulfilment of a lifelong wish of her grandfather, Ānaru.
The land at Umupuia was part of Ngāi Tai lands, some 60,000 acres, which included Papatoetoe, Ōtāhuhu, Howick, Papakura and Whitford. Rachael began a petition to have these lands returned to Ngāi Tai, but it was unsuccessful. Only 800 acres at Umupuia remain.
Rachael Zister was made a CBE in 1989, received the New Zealand 1990 Commemoration Medal, and in 1993 was awarded the New Zealand Suffrage Centennial Medal. She died on 22 May 1997 at Ōtāhuhu aged 103. William had died in 1978, and she was interred beside him at the Umupuia Māori cemetery.