Barça, playing without the injured Lionel Messi, remain 13 points ahead of Real Madrid who beat Athletic Bilbao, also by 3-0.
Thiago Alcantara got Barcelona going with a tidy finish on 20 minutes and the Spanish international then played in Cristian Tello to make it 2-0 just before the break.
Tello showed great pace and poise to register his second of the evening seven minutes after the restart and there was even a rare clean sheet for Barca despite the absence of Gerard Pique at the back.
"We are happy to get this result because La Romareda has been a difficult place to come for us in recent times," Thiago told Gol TV.
"I think the team in general has been complete in all facets, in both attack and defence."
Tito Vilanova made six changes from the side that started Wednesday's exacting Champions League clash with Paris Saint-Germain.
However, it was one of those not rested that caused a surprise as Xavi started a league game for the first time since early February.
Zaragoza had dropped into the relegation zone due to Deportivo La Coruna's win on Saturday and their lack of confidence having not won a game at all this year was in evidence as they failed to trouble a makeshift Barca defence throughout the first-half.
Yet, for all Barca's early possession, the opening goal arrived from one of the few occasions when Zaragoza might have been able to put the visiting defence under pressure, but instead Barca broke upfield from a home corner and a neat exchange of passes between Thiago and Sanchez allowed the midfielder to sweep home just his second goal of the season.
Thiago was involved again as Barca doubled their advantage six minutes before the break as this time he and Tello combined to allow the winger to run through on goal and he showed great composure to slot past Roberto.
Sanchez could even have had a third before the break but for a good reaction save by the Zaragoza keeper and the Chilean's luck was also out at the beginning of the second period as this time he lobbed Roberto only to see the ball come back off the bar.
The third Barça goal did arrive soon after though as Tello showed off his frightening speed once more to dash past Glenn Loovens and slot into the far corner.
Real Madrid remain 13 points behind the leaders after two goals and an assist from Cristiano Ronaldo guided them 3-0 win at Athletic Bilbao.
In contrast to Barcelona, Jose Mourinho named almost a full strength Madrid side and was rewarded when Ronaldo got the visitors off to the perfect start with a wonderful free-kick that dipped into the top corner.
However, Madrid also had to rely to great saves from Diego Lopez to deny Markel Susaeta and Ander Herrera as Athletic went onto boss the first-half.
Ronaldo sealed all three points for Los Blancos with 20 minutes to go though as he rose highest to bullet Xabi Alonso's free-kick into the far corner before the Portuguese slipped in Higuain to fire home the third from a narrow angle five minutes later.
Atletico Madrid kept up their chase of Real in second place with a 5-0 thrashing of Granada at the Vicente Calderon.
Diego Costa opened the scoring for Los Rojiblancos before a Radamel Falcao double and second-half goals from Raul Garcia and Filipe Luis sealed a first victory in three games for Diego Simeone's men.
Real Sociedad increased their advantage in fourth as two early goals from Imanol Agirretxe handed them a comfortable 2-0 win at Rayo Vallecano.