Complex sentence: The choice to visit Zagreb during political and cultural developments in SR Croatia that would culminate in the Croatian Spring, along with Nixon's praise for the spirit of Croatia "and his famous exclamation" Long live Croatia !
Split into simpler sentences: The choice to visit Zagreb coincided with political and cultural developments in SR Croatia that would culminate in the Croatian Spring. This, along with Nixon's praise for the spirit of Croatia "and the famous exclamation" Long live Croatia!