Complex sentence: OzonAction is a branch of the United Nations Environment Programme (UNEP) which has its main office in Paris, and is part of UNEP's Division of Technology, Industry and Economics (DTIE).
Split into simpler sentences: OzonAction is a branch of the United Nations Environment Programme (UNEP). This branch, which has its main office in Paris, is part of UNEP's Division of Technology, Industry and Economics (DTIE).