D-Zug meaning in International ?

Answer: What is Durchgangszug mean?

A Schnellzug is an express train in German-speaking countries, where it refers to trains that do not stop at all stations along a line. The term is used both generically and also as a specific train type. In Germany and Austria it is also referred to colloquially as a D-Zug, a short form of Durchgangszug ("through train"), and express train services were often given numbers preceded by the letter D. The similar term, snälltåg, was used in Sweden until January 1980.

On the railway networks operated by the Deutsche Bahn (DB), the Austrian Federal Railway (ÖBB) and the Swiss Federal Railways (SBB) today, express trains are divided into categories such as Eurocity, Intercity, Interregio etc. The DB still occasionally runs D-Zug services in night trains (D-Nacht), especially those to its eastern European neighbours, and as relief trains. Museum services running on DB routes are also given D-Zug numbers.

reference

Full Form	Category
Direkt-Zug	International
Durchgangszug	International