The Argentinean prodigy fired the hosts in front as early as the fifth minute before Alberto Zapater leveled the score four minutes later.
The impressive Messi resorted Barca's lead in the 11th minute and Andres Iniesta added the third in the 21st minute.
Rafael Marquez completed the rout just before the interval to hand Barcelona their second successive victory.
Ronaldinho was once again left out of Barcelona squad amid reports of a rift between the Brazilian playmaker and the Catalans' board.
Barcelona moved to third spot in the league table with 11 points while Zaragoza left 14th on five points.
Villarreal moved to the top after cruising past Racing Santander 2-0, thanks to two strikes from Turkish striker Nihat Kahveci and Italian frontman Giuseppe Rossi.
David Silva's brace helped Valencia edge past Getafe 2-1 and become joint leaders.