When booking flights it is essential that you check out that you have enough time between the flights so that you don't miss your connections!

Don't forget that Kuala Lumpur has 2 airports where travellers normally fly into and out of.  KUL is the airport code for both KLIA and KLIA2 terminals located at Sepang, and SZB is the code for Subang Airport / Skypark Terminal ( Sultan Abdul Aziz Shah Airport ) which once was the international airport until KUL opened.

KUL at Sepang = KLIA1 and KLIA2 terminals, it is only 1 airport and has been the main international airport since 1998 and is the home of Malaysia airlines and Air Asia. The majority of tourists and travellers will use the 2 terminals at this airport. There are 2 terminals at KUL. KLIA1 used by Malaysia Airlines and other international [national] carriers, and KLIA2 used by Air Asia. They are not separate airports, they are just different terminals. It is not possible to transit airside within KLIA1 and KLIA2.

KLIA1 and KLIA2 ARE the same airport!  Just different terminals.  Both terminals are coded KUL by IATA!

SZB at = Sultan Abdul Aziz Shah Airport aka Subang [International] Airport aka Skypark Terminal. Was the international airport from 1965 to 1998 when it had 3 terminals in use, only T3 is now in use and renamed as the Subang Skyway terminal. It is the home of FireFly and Berjaya Air, flying mainly domestic Malaysian routes and short routes into neighbouring Thailand / Indonesia.

KUL KLIA1 / KLIA2 is 40-60 minutes / 50 km south from Kuala Lumpur

SZB Subang is 30 minutes / 26km west of Kuala Lumpur

KUL KLIA1 / KLIA2 is 55 km from Subang / SZB - a journey between the 2 airports will take around 45 minutes.

This article covers how to get between the 2 terminals at KUL, KLIA1 and KLIA2  

The best way is via train.  KLIA1 and KLIA2 are both on the KLIA Express train route so are connected by a 3 mins train journey.