I'm from India. I intend to travel to Croatia and Italy, by flying from India to Croatia (outside Schengen), via a transit through Frankfurt. I will then fly to Italy from Croatia. When I apply for a Schengen visa from the Italian consulate, will my stay in the Schengen region be considered to have started from the time I transit through Frankfurt, or only when I arrive in Italy ? Would my itinerary be considered as 2 entries into the Schengen zone (since I leave the schengen zone when flying from Frankfurt to Croatia) ? I ask this because I need to have a valid, Multi entry Schengen visa to visit Croatia without a separate Croatian visa.
When you arrive at Frankfurt from India and immediately continue on a flight to Croatia, you will not enter the Shengen area as part of that transit. You will stay in the international transit area of the airport.
At least this is the case if both your flights are part of a single booked journey, such that you don't need to collect and re-check baggage.
If you need a reason to get a two-entry Schengen visa, you could either amend your plans with an overnight stopover in Frankfurt, or perhaps state in your application that you will book the Frankfurt-Croatia ticket separately and therefore need to enter Schengen to recheck baggage. If you can make the latter seem like a reasonable plan, given the choices of airlines, etc. you present in your itinerary, there's a good change that the Italian consulate would issue a 2-entry visa.
If you do need to enter Schengen in Frankfurt, then certainly you will need to exit it again to go to Croatia. Arriving in Italy later will be another entry.