Southampton booked an FA Cup fifth round tie against Liverpool with a 3-0 win over Watford on Tuesday, while Coventry’s 4-1 victory against Sheffield Wednesday secured a date with history makers Maidstone.
The Championship high-fliers, unbeaten in their last 24 games in all competitions, took the lead when Che Adams teed up Mara in the 52nd minute.
Mara doubled his tally six minutes later as the French youngster struck for the fifth time in his last nine appearances.
Adams completed the comfortable dismissal of second-tier Watford with a clinical finish 14 minutes from full-time.
Coventry will host National League South side Maidstone after Callum O’Hare’s double saw off Wednesday in another all-Championship replay.
It was the third meeting between Coventry and Wednesday in just 17 days.
The first of those encounters was marred by racist abuse directed at Coventry midfielder Kasey Palmer by a Wednesday fan.
Palmer opened the scoring in the third minute before Mark Robins’ men were pegged back by Bailey Cadamarteri’s equaliser.
Three goals in eight second-half minutes, including two from O’Hare and one from Haji Wright, ensured Coventry will host the lowest-ranked side left in the competition.
Maidstone became the first club from outside the top five tiers of English football to reach the FA Cup fifth round since Blyth Spartans in 1978 when they beat Ipswich 2-1 at Portman Road in one of the great recent cup upsets.
Leeds will travel to Aston Villa or Chelsea in the last 16 thanks to a 4-1 win at Championship rivals Plymouth.
Wilfried Gnonto’s 66th-minute strike put Leeds ahead at rain-lashed Home Park, but the advantage lasted just 12 minutes before Brendan Galloway equalised.
In extra-time, Crysencio Summerville curled home to put Leeds back in front, then set up Georginio Rutter to net the visitors’ third goal in the 111th minute.
Ryan Hardie’s own-goal in the 117th minute made it a happy journey back to Yorkshire for the Leeds fans who made the round trip of over 600 miles.
Leeds will discover their next opponents on Wednesday when Chelsea face Unai Emery’s men at Villa Park.
Nottingham Forest host second tier Bristol City in the other replay on Wednesday.
The fifth round ties will be held on February 26, 27 and 28.