How can a traveler shorten and combine prayers if Maghrib time has begun and he has not prayed Dhuhr and Asr? And should he pray four rak'ahs or two?

It is permissible for a traveler to shorten the four-rak'ah prayer to two rak'ahs. It is also permissible for him to combine the Dhuhr and Asr prayers, and the Maghrib and Isha prayers, performing them at the time of one of them. It is forbidden for him to delay a daytime prayer until night or vice-versa. If someone delays the Dhuhr and Asr prayers until Maghrib begins, he should pray Dhuhr then Asr as a make-up (qada'), then Maghrib as a current (ada') prayer. The make-up prayers should be performed in their proper sequence, just like current prayers, unless there is a fear that the time for the current prayer will expire.