Complex sentence: But they failed to conquer the provinces of Taguzgalpa and Tologalpa in today's northeast Honduras and western Nicaragua as well as much of the coast of Panamá and Costa Rica which also lay beyond their control, save a few key towns.
Split into simpler sentences: But they failed to conquer the provinces of Taguzgalpa and Tologalpa in today's northeast Honduras and western Nicaragua. Much of the coast of Panama and Costa Rica also lay beyond their control, save a few key towns.