The curry takeaways and restaurants around my places of work are full at lunchtime. I have Swiss colleagues at work and they love to go for a curry for lunch (the main meal of the day for them) with me. We go average 1.5 times per week together and at least once it is the curry place at "Talacker" opposite the Irish pub on Sihlstrasse.
Places like Mishio's, Tiffins in Seefeld (you will know them when you get here) do good business to my knowledge. Personally I think your best bet would be a prime location near some offices.
It is a very different market in terms of prices, portions & quality (it must be good quality fresh ingredients) and as some other responses indicate food hygiene courses and regulations would need to be met.
This company
www.startups.ch provide alot of information in English about starting a business here. I think for food business an Einzelfirma (sole trader) or a partnership, if you want to work together on the business, would be fine, but take advice on the matter, I am no expert.
I set up my sole trading firm a year ago here and it is absolutely buzzing. I have both Swiss & international customers so think about pitching to a wide audience and as I say, all the Swiss I know (the under 45s certainly) love a good curry too. Good luck and let me know how you go. I'd be interested to try some of your food.