In 1953 Henk van Zalinge built a HVZ based on a pre-war Alfa Romeo 6C-2300, with a self-made steel body. Very soon the old Alfa engine broke down and was replaced by a 2.5 litre Riley engine.
In 1954 he started to build his first Hirondelle, with a Porsche RSK engine in front of the Opel rear axle in a self-made chassis and with an aluminium body made by Rijnplaat. Originally the gearbox was from an MG TD, but soon this was replaced by an adapted Porsche gearbox.
The second Hirondelle was the shown car with DKW engine and self-made chassis and aluminium body. This one was indeed used for the Blériot race.
The third and last Hirondelle also had a DKW engine, with an aluminium body by Vermeulen (from Haarlem). This car looked more like a Formula racer.
Btw, there is a film by the Amsterdam photographer Ed van der Elsken where he drives a (normal) DKW and he visits Henk van Zalinge's workshop to get his engine tuned. Very noisy
Here a picture of the DKW-Hirondelle when it was still under construction: