The core of Zuidam’s compositional activities lies in the field of vocal music, particularly that of the musictheatre. It was Hans Werner Henze, who made Zuidam aware of his potential as an opera-composer and -librettist, and commissioned him to create a full-length opera for the Biennale für Neues Musiktheater in Munich, Germany. This resulted in Freeze, an opera based on the story of the Patricia Hearst-kidnap, which was realized in 1994 in a co-production with the Holland Festival and the Staatstheater Braunschweig. Soprano Susan Narucki performed the leading role of the piece, that prompted Klaus Umbach, music-critic of Der Spiegel to label Zuidam as “ein genialischer Hund”. A second opera, Rage d'amours, was commissioned by the Boston Symphony Orchestra and was premiered in August 2003 at Tanglewood, with the much acclaimed soprano Lucy Shelton as leading lady. Also on this occasion, the press responded with enthusiasm. The New York Times wrote: "a formidable work... a score that keeps you hooked... with Rage d'amours Mr. Zuidam announces himself as a composer to reckon with". Rage d'amours, which portrays the turbulent relationship of Johanna the Insane and Philip the Handsome, received its European premiere in June 2005 during the Holland Festival in Amsterdam, in a double-bill with Zuidam’s McGonagall-Lieder, with Claron McFadden, Barbara Hannigan and Young-Hee-Kim performing the leading roles, in a staging by Guy Cassiers. A new production of Rage d'amours will be premiered early in 2012 in Germany by director and choreographer Nanine Linning.
In 2006 the chamber-opera Der Hund was created, in a production of Muziektheater De Helling, directed by door Aat Ceelen, about the final hour of the Austrian suicidal misanthrope Otto Weininger. In 2009, Zuidam composed Adam in Ballingschap for De Nederlandse Opera and the Holland Festival, after Joost van den Vondel’s play from 1664, again staged by Guy Cassiers, with Claron McFadden and Thomas Oliemans performing the leading roles.
Zuidam's most recent opera Suster Bertken, about the life and poetry of a 15th-century anchoress from Utrecht, received its first, semi-staged performances in December 2010 with soprano Katrien Baerts in the title role and the ASKO-Schönberg Ensemble, conducted by Reinbert de Leeuw. Plans for a fully staged series of performances of Suster Bertken in 2012/13 are being developed.

In addition to this, Rob Zuidam composed a large number of works for orchestra, ensembles and soloists. Between 1991 en '98 for example, the four-movement orchestral work Trance Symphonies was created, and on a commission by the Michael Vyner Trust in London, he composed Sauvage Noble (2001), a concerto for oboe, horn and ensemble. The Royal Concertgebouw Orchestra commissioned Zuidam for Adam-Interludes, composed in 2008, to commemorate the birthday-centennial of Olivier Messiaen. (released on cd in 2010) The Japan Netherlands Society commissioned him to create Music for Viola, Piano and Ensemble, which received its first performance in November 2005 at Oji Hall, Tokyo, by Nobuko Imai, Tomoko Mukaiyama and the Viotta Ensemble. Also in 2005, Zuidam made an adaptation of Mozart’s Don Giovanni for the Dutch National Ballet, in collaboration with choreographer Krzysztof Pastor and dramaturge Carel Alphenaar, which until the present has received thirty performances in the Muziektheater in Amsterdam. Zuidam’s music was performed by, amongst others, the Royal Concertgebouw Orchestra, the Residentie Orchestra in The Hague, the Holland Symfonia, the German Ensemble Modern, the London Sinfonietta, the ASKO-Schönberg Ensemble, the Nederlands Kamerkoor, soloists such as Elliott Fisk, Peter Serkin and Benjamin Schmid, and conductors such as Reinbert de Leeuw, Oliver Knussen, Ingo Metzmacher, Otto Tausk. Peter Ruzicka, Stefan Asbury, Bradley Lubman, Markus Stenz en Richard Dufallo.

But, as stated before, the focal point of his compositional output is targeted at vocal music. The McGonagall-Lieder (1997-2000) for colorature-soprano and ensemble, Pancho Villa (1988-'90) voor mezzo-soprano and piano, Nella Città Dolente (1998) for vocal octet and particularly Calligramme/il pleut (1991, rev. 2009), for two female voices a cappella, belong to Zuidam’s most frequently performed works. He is currently working on a Requiem, for the Nederlands Kamerkoor and the ASKO-Schönberg Ensemble, and on the Canciones del alma, a large scale work for soprano and chamber-orchestra on poems by San Juan de la Cruz. Besides his work as a composer, Zuidam is also active as an essayist on music, a.o. for the Dutch newspaper NRC Handelsblad. Zuidam’s music is published by Albersen, in The Hague.