Complex sentence: The first large achievement by the club was winning the "Goblet of the King" during the 1919/20 season, not long after the tournaments foundation, the same season Lucca won the Regional cup of Tuscany.
Split into simpler sentences: The first large achievement by the club was winning the "Goblet of the King" during the 1919/20 season, not long after the tournaments foundation. The same season Lucca won the Regional cup of Tuscany.