Most regies don’t like to accept that you sublet unless you have a valid reason but you can try. If you do a search in the forums using the words ‘subletting,sublet etc’ you can find forums already started with information.

http://www.asloca.ch/questions-r%C3%A9ponses-faq

I have some experience of this. In fact it is the opposite (in Vaud at least)

I have the right to sublet my apartment , as far as I indicated in my lessor conditions sublease .

Transleated with Google:

Yes , but you must seek written permission from the landlord to be able to sublet . It can not refuse , unless valid reasons , if you communicate to him the terms of the sublease ( identity of the sub- tenant, the rent sublease ) . It is still necessary that the conditions for subletting are not abusive ( not sublet double the price of the main location! ) . In case of unjustified refusal of the lessor, it is necessary to refer the matter to conciliation that the conditions sublease are not abusive .

As main tenant , you remain liable to your landlord for all obligations under the lease , you fully answer the acts of the sub-tenant ( payment of rent, damage to housing, behavior in the building) . Make sure it has liability insurance , make him sign a written lease and make rent - establish a guarantee from a bank ( security, which must be included in the written contract ) .

So they cannot refuse unless they have a valid reason.

Use Asloca, as mentioned by Oongah, they will help you, and pay attention to the part about your responsability.

Richard is very right about sub-lease agreements.

One thing you need to be carefull is that even if a Regie dont want to sublease, you can still submit 3 persons to the Regie and 'I beleive' they either need to accept one or more or they must provide a valid reason why they dont accept.

Some Regie also will accept total takeover of a Lease, just to simplify. Especially if your not Swiss and live in say USA or spain.