Hi Elena,
In answer to your question, I am a descendant of the Inzunza family that lived in Mocorito, Sinaloa, from the 17th century onwards. The family is mentioned in books like
Eustaquio Buelna's Apuntes sobre la Historia de Sinaloa (circa 1885), Jose Ramon
Velazquez' Apuntes de Mocorito (1994) and Gustavo
Aguilar Aguilar and Wilfredo
Ibarra Escobar's El Origen de la Banca en Sinaloa (1998). The last tome mentions at least one
Esquerra (with an a). My grandfather Pedro Inzunza
Gaxiola had a business relationship with an
Esquer in Sinaloa at the end of the 19th century. My feeling is that the
Ezquerro,
Esquerra and
Esquer families may all be branches of the same
Spanish settlers in Sinaloa -- I have seen documents where in fact the same gentleman will be referenced in the text of the document with a "z" and yet he signs his name with a definitive "s".