Complex sentence: Singapore has a long-standing relationship with both the United Nations Environment Programme and the Economic and Social Commission for Asia and the Pacific, participating actively in the "East Asian Seas Regional Programme" of the 1974 UNEP-initiated Regional Seas Programme.
Split into simpler sentences: Singapore has a long-standing relationship with both the United Nations Environment Programme and the Economic and Social Commission for Asia and the Pacific. Singapore participates actively in the "East Asian Seas Regional Programme" of the 1974 UNEP-initiated Regional Seas Programme.