Just to be clear, without the UK transit visa, your friend will not be allowed to board the Zurich to London flight. His options, therefore, are only one: to change his itinerary so as to not pass through the UK.
There is no reasonable way to obtain a UK visa within "hours". It requires filing a visa application and sending out your passport and paperwork to a consulate and waiting several days.
In some countries there is a super priority visa service which can return a UK visa decision within 24 hours; it can cost between £500-£1000 depending on country. But this isn't going to happen within the time of a flight layover, and it will probably cost as much or less to change the flight itinerary anyway.
He's already in Schengen; there are flights to India from a variety of European airports in the Schengen area that either fly direct or transit via somewhere reasonable like UAE. There are many, many options. If he's flying on Jet Airways/Swissair they should be able to re-route him through AMS, i.e. ZRH-AMS-DEL. Even throwing away the entire ticket and booking something new might be an option; I see a last minute ZRH-SVO-DEL on
Aeroflot for CHF357 one way.