This is the 98th most frequent Dutch word.
zelfs
"Even."
The word 'zelfs' here introduces a condition that emphasizes an exception or unexpected situation, highlighting persistence or determination despite circumstances.
Zelfs als het regent, gaan we wandelen.
Even if it rains, we go for a walk.
In this example, 'zelfs' is used to stress the unexpected nature of Peter being late, someone who is known for never being late.
Zelfs Peter, die nooit laat is, kwam vandaag te laat.
Even Peter, who is never late, was late today.
Here, 'zelfs' focuses on expressing the speaker's accomplishment (solving the hardest problem) that might have been surprising or impressive.