Nothing will go right for any party in this war. Tough country, tough locals, and invisible tough natives.
... but Venezuela is well armed.
Here is a list: https://en.wikipedia.org/wiki/List_of_equipment_of_the_Venezuelan_Army
They have plenty of armor that the darts from the blowpipes of invisible natives won’t penetrate.
Brazil should be able to wipe the floor with them if we compare country sizes, but can they bring their heavy weapons where these need to be?