Germany could certainly have beaten the Swiss army, if nothing else simple numerical superiority would ensure that. Afterwards Switzerland would be occupied and added as an other Gau to Germany.
If you define that as succes then yes Switzerland could have been succesfully invaded and occupied.
However during the Invasion:
- The transport routes from Germany to Italy would be destroyed.
- A large part of the Swiss industry would be destroyed and what survived would be subject to allied bombardation.
- An important financial hub which allowed the Germans to change the gold reserves of stolen countries into clean currency would be gone.
After the Invasion Switzerland would be full of partisan groups and require a constant garrison, certainly not as great as France or the territories in the east, but it would nonetheless be a further drain on Germanys resources.
So if you define succesfull as "strengthening Germany" then no it couldn't.
If you define that as succes then yes Switzerland could have been succesfully invaded and occupied.
However during the Invasion:
- The transport routes from Germany to Italy would be destroyed.
- A large part of the Swiss industry would be destroyed and what survived would be subject to allied bombardation.
- An important financial hub which allowed the Germans to change the gold reserves of stolen countries into clean currency would be gone.
After the Invasion Switzerland would be full of partisan groups and require a constant garrison, certainly not as great as France or the territories in the east, but it would nonetheless be a further drain on Germanys resources.
So if you define succesfull as "strengthening Germany" then no it couldn't.