Complex sentence: In 1974, at the age of 19 years, he won the International Tchaikovsky Competition, still being the youngest in its category ever, and in the same year he successfully substituted for Sviatoslav Richter at the Salzburg Festival.
Split into simpler sentences: In 1974, at the age of 19 years and still being the youngest in its category ever, he won the International Tchaikovsky Competition. In the same year he successfully substituted for Sviatoslav Richter at the Salzburg Festival.