When Zemlinsky mounted the conductor's podium, the small inconspicuous man became a musician of immense authority, presence and physical radiance. "Even the movement of his shoulders when he raises the baton is music", wrote Franz Werfel.
In Vienna Zemlinsky was highly regarded as a conductor but more especially in Prague and on tours he later undertook throughout Europe. His contemporaries appreciated in particular his intellectual perception, sense of sound and the dramatic instinct of his conducting. This was not characterised by technical virtuosity or radical interpretations but by Zemlinsky's ability to allow the music to speak for itself. "Zemlinsky feels the music and shapes it by feeling it. He is an artist among the musicians", was how Erich Steinhard described it.
For Schoenberg his music-making was "above all an aesthetic, or even more than that: a moral pleasure" and he admired his "natural, unforced and obvious greatness". However, Zemlinsky received probably the most wonderful praise long after his death, when in 1964 Igor Stravinsky recalled, "But I do believe that of all the conductors I have heard, I would choose Alexander Zemlinsky as the most outstanding, and this is a mature verdict." Zemlinsky felt most at home in German repertoire: operas by Strauss, Wagner, Schreker and Weber; orchestral works by Beethoven, Brahms, Strauss and Mahler were at the centre of his work — and again and again Mozart, for whom he had a special "little hand". "I remember a performance of Le nozze di Figaro in Prague as being the most satisfying opera performance I ever heard." (Stravinsky)
Zemlinsky was especially committed to promoting contemporary works. In particular in Prague where, by virtue of his position, he was able to arrange the performance of many new operas and orchestral works, for instance much music by Schoenberg as well as compositions by Berg, Bartók, Dukas, Ravel, Korngold, Krenek, Janácek, Schulhoff, Hindemith, Honegger, Milhaud and Weill.