Zen has a promotion on Qatar where fares have been reduced for travel period between now and March 14, April 1 and 12 June, and 28 Jul -19 September. Fares are slightly higher between 15 March – 31 March for the spring break, and 20 September - 9 December because of Dashain and Tihar. Tickets must be purchased by 29 February.
Note, some of these tickets are non-refundable, and date change penalties are very high. If there is a layover over 8 hours, a complimentary hotel is usually provided (in one direction only).