Russian emperors are usually referred to as "Tsars" or "Czars". However, while the first spelling (Tsar) utilises the standard English transliteration of the Cyrillic ц as ts, the second transliteration does not.
None of the Slavic languages that use the Latin script render their ц phoneme equivalent as "cz". Polish, Czech and Slovak render the phoneme as c instead. cz renders as a completely different phoneme in Polish, and does not exist in Czech or Slovak.
Where then, did the "cz" spelling originate from?