Complex sentence: He returned to international politics and, as an international financier, he proved to be instrumental in the economic recovery of several Central and Eastern European nations, helping to stabilise the Polish zloty in 1927, and the Romanian leu in 1928.
Split into simpler sentences: He returned to international politics several years later and, as an international financer, proved to be instrumental to the economic recovery of several Central and Eastern European nations. He helped stabilising the Polish zloty in 1927, and the Romanian leu in 1928.