His parents moved in 1967 from Poland to Denmark, where Zandberg was born in 1979. In 1985 his family moved back to Poland. After studying history at Warsaw University, he received his doctorate for his dissertation about British and German left-wing social democratic movements. He also studied computer science at Polish-Japanese computing academy.
As a student he devoted himself to politics. On November 14, 2001, he published an article in the "Gazeta Wyborcza" daily newspaper written together with civil rights activist Jacek Kuroń on the topic of social justice in Poland.
He was elected chairman of the youth wing (Forum Młodych) of the Labour United party (Unia Pracy), was a member of the executive of this party and founded the Federation of Young Socialists (Młodzi Socjaliści).
In May 2015, he became one of the founders of Partia Razem, a new political party, and was elected to the nine-member Board, together with Jakub Baran, Aleksandra Cacha, Alicja Czubek, Maciej Konieczny, Magdalena Malińska, Mateusz Mirys, Katarzyna Paprota, and Marcelina Zawisza.
Zandberg was placed on the first place on Razem's Warsaw candidate list of the Sejm elections in October 2015. As a Razem party representative during a television debate before the 2015 parliamentary elections, held in Poland on October 25, he represented the smallest of the eight parties. Among other positions, he was the only one of the eight panelists who pleaded for an unconditional acceptance of Syrian war refugees in Poland. Following the debate, some of the media declared him the winner of this discussion, and his appearance at the debate generated more media interest in him and his party in the following days. Zandberg received personally 49,711 votes, but his party won only 3.62 percent of votes, so did not gain any seats in the Sejm.
While some commentators claimed that the increase in popularity of Razem was at the expense of the United Left coalition (among others consisting of SLD, PPS, Greens and Twój Ruch), which also did not win any seats, resulting in neither left-wing party being represented in the new parliament, others, including United Left leader Barbara Nowacka, disagreed with that assessment, pointing out that Razem attracted mostly new electorate, and few of its voters had voted for SLD or Twój Ruch in previous elections and that the decrease in popularity of United Left's member parties had been a steady process over the years due to past errors.
He is married and has two children. As of 2015, he works professionally as a computer programmer.