Born Xiaodan Zheng to a musical family in Shenyang, China. She is one of seven professional cellists on her paternal side. Her family moved to Russia when she was 9 years old where she studied cello and piano at the Glinka School for Gifted Children in Novosibirsk, Siberia and later, at the Moscow Tchaikovsky Pre-Conservatory. Her family immigrated to New York in 1998, at which time she continued her studies at the Juilliard School Pre-College Division and the LaGuardia High School for Music & Arts and Performing Arts. Upon graduation, and at the recommendation of Itzhak Perlman and his wife, Xiaodan went on to study with Ron Leonard at the University of Southern California's Thoronton School of Music. Helen's former cello teachers include Alexei Seleznev in Moscow, André Emelianoff at Juilliard, and her father James Zheng.
Helen's achievements include winning the Juilliard Pre-College Concerto Competition, Juilliard Honor Strings Competition, Lincoln Center Chamber Music Society Young Artist Award, LaGuardia High School for Music, Arts, & Performing Arts Concerto Competition, the ASCAP Ira Gershwin Award, second prize in Corpus Christi Young Artist Competition, and first prize at the Great Neck Young Artist Competition in New York for both Solo and Chamber Music categories. Her piano trio at Juilliard was featured on WQXR 93.6 Radio NY with host Robert Sherman and NPR "From the Top" show with host Christopher O'Riley. During her school years, Helen spent her summers at the Perlman Music Program, Tanglewood Music Festival, Pacific Music Festival (Japan), Verbier Music Festival & Academy (Switzerland), Beijing International Music Festival, Bowdoin Music Festival, and Musicorda.
Upon graduating from USC, Helen won auditions for the Long Beach Symphony Orchestra, New West Symphony Orchestra, the Santa Barbara Symphony, and the San Diego Chamber Orchestra. She was also a regular substitute cellist for the Pacific Symphony Orchestra and the San Diego Symphony. Between 2009 - 2012, Helen was the appointed Principal Cellist of the Tucson Symphony Orchestra and was given tenure for her outstanding leadership. In 2010, Helen won a position with the Los Angeles Opera Orchestra, and in 2012 she obtained a tenured position with the Hollywood Bowl Orchestra which prompted her permanent move back to Los Angeles.
As a professional cellist, Helen has collaborated in concerts with artists such as Itzhak Perlman, Pinchas Zukerman, Yo-Yo Ma, Yefim Bronfman, Lang Lang, James Levine, Renée Fleming, Plácido Domingo, Bryn Terfel, Andrea Bocelli, John Williams, Bonnie Raitt, Reba McEntire, Willie Nelson, the Blue Man Group, and Earth, Wind & Fire. She has performed at Carnegie Hall, Avery Fischer Hall, Juilliard Theater, Alice Tully Hall, the Sydney Opera House, Wiener Musikverein (Vienna), Mann Auditorium (Tel Aviv), National Arts Centre (Ottawa, Canada), National Grand Theater (Beijing), Rachmaninoff Hall, and the Tchaikovsky Concert Hall (Moscow). Helen has appeared as a guest artists with the California Quartet, Salastina Music Society, Capitol Ensemble, and TEMPO New Music Ensemble.
Her album "Grieg and Prokofiev" (credited as Xiao-Dan Zheng, with pianist Clara Yang) under Albany Records label was awarded the 2014 Global Music Award Silver Medal. She is also part of the recording music industry for motion pictures and television in Hollywood with recent projects including La La Land, Finding Dory, Pirates of the Caribbean: Dead Men Tell No Tales, Birth of a Nation, Star Wars episode VIII, Hidden Figures, Fences, Cars 3, Empire (TV), and Agents of the S.H.I.E.L.D. (TV).
Helen established her stage name as Helen Z. Altenbach in 2016 incorporating her married name. Helen lives in Los Angeles with her Swiss-born husband and shelter-rescued cats.