To lose 40 lbs in 60 days, you're looking at 1.5 lbs lost per day, which is A LOT.
The only way you're going to achieve that is if you are at the moment in the 'obese' category, as its not easy to create such a massive calorie deficit to create that kind of weight loss in any healthy way if you're just a bit overweight.
If you want to play it safe, eat no less than 1,200 calories as a woman or 1,500 calories as a guy each day.
Further, do 1 hour of cardio every day to burn an additional 500 calories.
Whatever weight loss you achieve with this is going to be your optimal rate, I would not push your body past this....
Ideally you should be looking for 2lbs of weight loss each week.
You can expect more loss if you weigh more though...