Complex sentence: The main city of the Sagarmatha zone is Triyuga "Gaighat" (inner Terai) other towns of the Sagarmatha hill area are Katari, Okhaldunga, Diktel, Salleri, Namchebajar, while Lahan, Rajbiraj, and Sirah are in the outer Terai.
Split into simpler sentences: The main city of the Sagarmatha zone is Triyuga "Gaighat" (inner Terai). Other towns of the Sagarmatha hill area are Katari, Okhaldunga, Diktel, Salleri, Namchebajar, while Lahan, Rajbiraj, and Sirah are in the outer Terai.