what is the feminine form of the title mentioned above?
Sultana
Sultan
As a feminine form of "sultan", used by Westerners, is Sultana or Sultanah and this title has been used legally for some (not all) Muslim women monarchs and sultan's mothers and chief consorts. 
who fought anglo-zanzibar war? Great Britain and the Zanzibar Sultanate why did they fight the said war? The British authorities preferred Hamud bin Muhammed as Sultan than Khalid bin Barghash
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Sultan [SEP] Feminine forms
As a feminine form of "sultan", used by Westerners, is Sultana or Sultanah and this title has been used legally for some (not all) Muslim women monarchs and sultan's mothers and chief consorts. However, Turkish and Ottoman Turkish also uses "sultan" for imperial lady, as Turkish grammar—which is influenced by Persian grammar—uses the same words for both women and men. However, this styling misconstrues the roles of wives of sultans. In a similar usage, the wife of a German field marshal might be styled "Frau Feldmarschall" (similarly, in French, constructions of the type "madame la maréchale" are quite common). The female leaders in Muslim history are correctly known as "sultanas".