Complex sentence: In 1942 Willy Vandersteen illustrated the pro-occupation book "Zóó zag Brussel de Dietsche Militanten" under the pen name Kaproen After the war Willy denied being Kaproen and he was not persecuted for his collaboration with the Nazi's, including antisemitic drawings.
Split into simpler sentences: In 1942 Willy Vandersteen illustrated the pro-occupation book "Zóó zag Brussel de Dietsche Militanten" under the pen name Kaproen. Vandersteen was not persecuted for his collaboration with the Nazi's that included for publishing antisemitic drawings.