Caruso converted from close range in the 90th minute to draw Huracan level at 2-2 with Crucero del Norte on Wednesday, forcing a shootout, and Monzon made the decisive save to see the home side triumph 5-4 on penalties.
The first four spot-kicks went in but after Huracan had their next two penalties saved to trail 3-2, Crucero missed twice, including an inexplicable chip over the bar, allowing the home side to force sudden death through Juan Arraya.
Leonardo Zaragoza and Lucas Villafanez scored with Huracan's next two efforts and then Monzon saved Franco Cabrera's spot-kick to secure a berth in the round of 32.
Earlier, Caruso scored his first goal from the spot in the eighth minute after being fouled in the box but a stunning free-kick from Diego Torres saw Crucero draw level before half-time.
A diving header from Claudio Fileppi took the visitors in front on the hour-mark but when Mauro Milano's free-kick came back off the bar in the final minute, Caruso was on hand to knock home the rebound.
In other Copa Argentina results, Banfield thrashed Aldosivi 3-0 with Cristian Molina scoring a double, while Douglas Haig triumphed 3-0 over Boca Unidos in a shootout after a 1-1 draw.
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