as you can see here tehsil or taluk is not usually translated
http://en.wikipedia.org/wiki/Tehsil

Zila / Zilla can be translated as district
http://cyberjournalist.org.in/links4.html

In British English, the terms "Tehsil" and "Zilla" can be translated as "county" and "district" respectively.

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Note added at 36 मिनट (2008-06-28 12:07:30 GMT)
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Please note that these terms are not the exact translations.

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Note added at 41 मिनट (2008-06-28 12:12:46 GMT)
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"Since these terms are unfamiliar to English speakers outside of the subcontinent, the word county has sometimes been provided as a gloss, on the basis that a tehsil, like a county, is an administrative unit hierarchically above the local city, town, or village, but subordinate to a larger state or province." (Source: http://en.wikipedia.org/wiki/Tehsil)

'tehsil' term has come from the Mughal administrative system in India. This term, though in vogue for some time in the standard parlance of the British regime in India, was later substituted with the term 'subdivision' which is equivalent of 'tehsil'. 'Thesil', however is still used in the educated Hindi speaking mass to refer to "subdivision".

Subdivision is proper English equivalent of 'tehsil'.

'zilla' is equivalent of 'district', as noted by my friends above.

as per Oxford Hindi English dictionary a tehsil is a revenue district while zilla is an administrative district