Complex sentence: Both Coahuila and Texas seceded from Mexico because of Santa Anna's attempts to centralize the government, with Texas forming the Republic of Texas and Coahuila joining with Nuevo León, and Tamaulipas to form the short-lived Republic of the Rio Grande.
Split into simpler sentences: Both Coahuila and Texas seceded from Mexico because of Santa Anna's attempts to centralize the government. Coahuila joined with Nuevo León, and Tamaulipas to form the short-lived Republic of the Rio Grande.