A 1-1 draw at Santa Fe was enough for defending champions Mineiro to seal their progression from Group 4.
The Brazilian giants (nine points, +2 goal difference) may yet finish second in the group, with Zamora (seven, +1), Santa Fe (five, +0) and Nacional Asuncion (5, -3) behind them.
But a draw was all they needed at the Estadio El Campin, and they set it up early on.
Jo and Guilherme played a lovely one-two just outside the area and the latter finished with a smart low shot past Camilo Vargas on eight minutes.
The Colombians would make for a nervous finish, however, as they pulled a goal back in the 63rd minute.
Dario Mosquera's wonderful cross from the left found Jefferson Cuero unmarked and the attacker headed in from close range.
With a trip to Asuncion on the final matchday, Santa Fe will fancy their chances of progressing despite failing to find a winning goal against Mineiro.
On a good day for the Brazilian sides, Cruzeiro kept their chances alive in Group 5 with a 2-0 win at Universidad Chile.
Bruno Rodrigo and Miguel Samudio scored first-half goals at the Estadio Nacional Julio Martinez Pradanos.
Both teams finished the encounter with 10 men as Cruzeiro (seven, +3) closed in on Defensor Sporting (10, +6) and Universidad Chile (nine, -3).
Real Garcilaso (three, -6) are bottom of the group.
Needing a win, Cruzeiro took a 16th-minute lead as Rodrigo headed in a Dagoberto free-kick from the right.
The lead was doubled five minutes before half-time after a fine team move which led to Ricardo Goulart playing in Samudio, who finished well in the one-on-one.
Universidad's Matias Caruzzo and Samudio were both sent off in the dying stages.
