This is the 15663rd most frequent German word.
zeitgleichen
"Zeitgleichen" means "to synchronize or occur simultaneously."
In this sentence, 'zeitgleiche' is an adjective describing the noun 'Erscheinen', meaning that the appearance of the books occurred at the same time, emphasizing simultaneity.
Das zeitgleiche Erscheinen der beiden Bücher überraschte die Leser.
The simultaneous release of the two books surprised the readers.
Here, 'zeitgleich' is used as an adverb to describe the verb 'veranstaltet', indicating that the events took place at the same time in different locations.
Die Konferenz wurde zeitgleich in mehreren Städten auf der ganzen Welt veranstaltet.
The conference was held simultaneously in multiple cities around the world.
In this example, 'zeitgleich' is functioning adverbially in the subordinate clause to express that their arrival and the train's arrival occurred concurrently.