Which projection is this data in?

Obviously the data is in UTM32 including the number of the zone. You can strip the 32 in front of your x-coord away as it is explicitely given by the provided CRS. However QGIS should be able to deal with this if you config that reference-system.

What you use as boundary seems like UTM33 without zonal extension. The same values with zonal extension would be 33,426,167.5 and 33,650,147.9 respectivly. Here you can see that you´re indeed using different CRS for your map and your data. You can transform either your map to UTM32 or your data to UTM33 to get comparable results.

As an aside the y-coords are not affected by the zone you´re in.

EDIT: So what does this x-coordinate actually mean? It is the difference to the middle-meridian of the appropriate zone - in your case either zone 32 or 33 - plus a value of 500km to avoid negative values. So in your example a value of 33,426,167.5 means that you´re in zone 33 and located 74km west of the middle-meridian (426 - 500 = -74 --> west). 33,650,147.9 therefor means you´re 150km (650 - 500 = 150 --> east) from the middle-meridian.

When coordinates make no sense, you can try the Null Island Algorithm: take those coordinates, transform them to all the available CRSs, and plot the results in a map.