Left hand (from viewers side), the larger one is the Czech 47mm KPÚV vz. 38. Yes, that's the gun fitted to the Pzjgr I. It's missing the muzzle brake.
The other two look like the 37mm KPÚV vz. 34, another Czech weapon. The muzzle break being the giveaway. I've seen examples of those in Peru and IIRC they had one in the Bogotá military museum in Colombia.