That first article is curious in that it has a passing reference to Electrologica without discussing it in any detail. Curious because that was the main, if not only, Dutch manufacturer of computers in that era.
The ZEBRA is the microprogrammed computer mentioned in the first note, I’m pretty sure.
On the Kirchoff adder mentioned in the first article, I wonder if the inventor mentioned actually is the inventor. It is described by name (but no mention of Kosten) in the text of the computer design course taught by A. van Wijngaarden at the MC Amsterdam, february 1948 – see document CR-3 in the CWI archive.