OK, I started with the Czech version which maps almost all keys to Czech characters. I kept all 1:1 entries like a=a (doesn't hurt) and changed only z=y and y=z. And of course the double entries for our German Umlaut vowels äüöÄÖÜ plus ss=ß, ee=€, qq=@, ..=,
Obviously, 1:1 entries may be omitted. I left them in to provide a default matrix for other languages and their specific keyboard layout.