there is an ms. violin concerto (1905-1906) - and other works - by Zsolt at the Sze. Library Budapest, I think, according to the Nektar.Oszk.Hu catalog. (A "Zong. Quintett" is listed in manuscript also, first movement only, date "1908. III. 4"- is that a string or a piano quintet, or something else? Interesting if they have the ms. of the piano quintet...)