Complex sentence: Greece's EU membership, coupled with a shared border with Turkey, means the country sees massive flows of illegal immigrants looking to enter the EU; traffickers also use Greece not only as a destination but a transit stop on the way to Western Europe.
Split into simpler sentences: Greece's European Union membership, coupled with a shared border with Turkey, means the country sees massive flows of illegal immigrants looking to enter the EU. Traffickers also use Greece not only as a destination but a transit stop on the way to Western Europe.