[2] Returning to Switzerland, he premiered several of his own light dramas and comedies, such as "Du kannst mich nicht verlassen" ("You can't leave me"),[3] at the Zurich Playhouse ("Schauspielhaus"),[1] where he also staged "Bei Kerzenlicht" ("By candlelight") by Siegfried Geyer and "Reiner Tisch" ("Spring Cleaning") by Frederick Lonsdale.
At a time when politics were becoming increasingly polarised, and many of the political trends seemed to be pointing in a wrong direction, Lesch was clear that he could not opt out of public debate: "The humorist who does not remain a moralist will be left trading only in sensation and farce" (Der Humorist, der nicht ein Moralist bleibt, wird zum Possenreisser und Geschäftemacher").
As the Cornichon's artistic director he did not hesitate to include material critical of the fascist states by which Switzerland was surrounded on almost three sides, to the north, east and south.
On 14 November 1935 his stage play, "Cäsar in Rüblikon", had its premier at the Zurich Playhouse ("Schauspielhaus") in a production directed by Leopold Lindtberg.
", the stage piece was a "dialect comedy", which connected its diverse elements with a consistent antifascist theme: the inhabitants of Rüblikon get rid of their Minister-president who has become a despot after the German model.
He tried - with little success - to promote politically critical pieces such as Werner Johannes Guggenheim's anti-Nazi "Erziehung zum Menschen" (loosely "Educating people").
Probably his most notable theatrical contribution from this period was the text (in Swiss German) for Paul Burkhard's die Kleine Niederdorfoper which had its premier on 31 December 1951 at the Schauspielhaus Zürich.
The marriage broke down progressively during the early 1940s, and Mathilde, who had met Herbert Crüger in 1939 and at some stage had married him as her third husband, moved to Germany in 1947, taking Karin with her, after which Lesch was cut off from his daughter.