Gualberto Mojica gave Oriente victory in their first round first leg against Nacional with a scorching strike just after the half-hour.
The side from Santa Cruz in central Bolivia have not qualified for the group stage of South America's premier club competition since 2011.
On Tuesday in Santa Cruz, the home side scored the only goal of the game in the 33rd minute when midfielder Mojica ran onto Juan Quero's pass in the penalty area and thrashed the ball inside the far post.
In the other first-round first leg, Morelia defeated Santa Fe 2-1 in Mexico, with the Colombian club's late away goal setting up an interesting second clash.
Zamorano strolled past a couple of defenders to score the Mexican hosts' second goal in the 66th minute but Santa Fe gave themselves hope ahead of next week's second leg when Omar Perez converted a penalty with five minutes remaining.
