Zaragoza came into the match having taken just 27 points from 30 matches and occupying 18th place.
And their performance replicated their standing as Tito Vilanova's team - 13 points clear of second-placed Real Madrid - dominated from the off.
Barcelona made seven changes from the side who progressed to the semi-finals of the Champions League this week but it made little difference as they dominated from the first minute to the last.
Cristiano Ronaldo scored twice as Real Madrid coasted to a comfortable 3-0 win over Athletic Bilbao.
Ronaldo struck with a fine free-kick in the second minute before heading a second after 69 minutes.
Gonzalo Higuain scored a third for Jose Mourinho's side while defeat left Bilbao eight points above the relegation zone.
Radamel Falcao scored twice as Atletico Madrid continued their bid for a top-two finish in the La Liga with a comprehensive 5-0 home win over Granada.
Falcao, who was the centre of more transfer speculation this week with Manchester United mooted as a possible destination this summer, struck in the 27th and 47th minutes to take his tally to 30 in all competitions this season.
Diego Costa, Raul Garcia and Filipe Luis were also on the scoresheet as Diego Simeone's men made it 14 wins from 16 league matches at the Vicente Calderon this season.
The win also keeps the pressure on City rivals Real, who are three points clear with seven matches left.
Real Sociedad are a further 11 points back in fourth as their outstanding run of form continued with a convincing 2-0 win away to Rayo Vallecano.
Two goals by Imanol Agirretxe in the opening 14 minutes set the Basque side on their way to victory and although they took their foot off the gas somewhat in the second half, they were always in control of the game.
It was their fourth win in their last seven and they are four points clear of Malaga and Valencia.
Meanwhile on Monday, Giovani Dos Santos gave Mallorca a life-line by scoring a last-minute winner against fellow relegation rivals Celta Vigo to claim a 1-0 win.
A match of few clear cut chances looked to be heading for a draw until Mallorca launched a flurry of attacks late on and the Mexico international bundled the ball over the line after Celta goalkeeper Javi Varas failed to hold onto a header by Tomer Hemed.
The result means the Islanders move off the bottom of the La Liga table, displacing Celta in 19th place and moving three points clear of the Galicians, and now they are just one point from safety.
Sergio Garcia's last-gasp strike rescued a point for Espanyol in a thrilling 3-3 draw at home to Valencia in La Liga.
Mubarak Wakaso opened the scoring for the hosts on the stroke of half-time but Sergio Canales levelled shortly after the restart.
The real drama was reserved for the closing stages of the match, however, with Joan Verdu putting Espanyol ahead again in the 82nd minute before his effort was cancelled out by Jonas fine minutes later.
Roberto Soldado gave Valencia the lead in injury time but there was still time for more drama as Garcia scored in the 94th minute to snatch the draw.
The result means Espanyol overtake Levante in 11th place, while Valencia missed the chance to reclaim fourth spot from Real Sociedad, who play Rayo Vallecano on Sunday.
Deportivo La Coruna took another big step towards survival after making it four wins on the trot with an impressive 4-0 victory at Levante.
The game was as good as over inside the opening half-hour as Depor struck three times through Juan Carlos Valeron, Luis Pizzi and Nelson Oliveira.
Bruno Gama put the icing on the cake with a fourth goal late on as the in-form Galicians climbed out of the relegation zone for the first time since November.
Real Valladolid staged a second-half turnaround to overcome 10-man Getafe 2-1 for their first home win since January.
Paco Alcacer gave the visitors an undeserved lead moments before half-time but goals by Oscar Ramos and Javi Guerra in quick succession turned the match around before Alexis Ruano was sent off for Getafe.
In the late match, Malaga's week to forget ended on a high as Julio Baptista's injury-time goal secured a 1-0 win over Osasuna.
Manuel Pellegrini's side were dumped out of the Champions League at the quarter-final stage on Tuesday thanks to Borussia Dortmund's injury-time heroics, but returned to winning ways on Saturday night to climb to fifth place in the standings.
In Friday's only game, Real Betis produced an astonishing comeback to recover from three goals down and hold local rivals Sevilla to a 3-3 draw, after goals from Dorlan Pabon, Ruben Castro and Nosa Igiebor cancelled out an Ivan Rakitic brace and a strike from Alvaro Negredo in the first half.
Monday's La Liga Fixture
Sunday's La Liga Result(s)
Saturday's La Liga Result(s)
Friday's La Liga Result(s)