Is the nakedness of a disbelieving woman only the two private parts and the breasts? And what is the evidence for that in the four schools of thought?

It is obligatory to be certain about the prohibition of looking at the 'awrah (private parts) of disbelieving women, for the verses and hadiths do not differentiate between a Muslim woman and a disbelieving woman, as in His (Allah's) saying: "Say to the believing men that they should lower their gaze and guard their modesty." The reason for which looking at the 'awrah of a Muslim woman is prohibited is also present in a disbelieving woman, which is to block the means to temptation (fitnah). Indeed, Al-Hasan (definition) commanded his brother to lower his gaze upon seeing unveiled women of the non-Arabs. There is no disagreement among scholars regarding the prohibition of looking at women with lust, whether they are Muslim or disbelieving, because looking at the ghaleez 'awrat (major private parts) is usually not free from lust.