Complex sentence: Portugal's central bank is the "Banco de Portugal", which forms part of the European System of Central Banks, and the major stock exchange is the Euronext Lisbon, which belongs to the NYSE Euronext, the first global stock exchange.
Split into simpler sentences: Portugal's central bank is the "Banco de Portugal", which is part of the European System of Central Banks. The major stock exchange is the Euronext Lisbon which is part of the NYSE Euronext, the first global stock exchange.