What spanish word starts with z?

Such Words would usually start with za, zo, zu (the same sound with "ze" or "zi" would normally be spelled "ce" and "ci"; some first and last names are notable exceptions). Examples are:

zorro (fox), zapato (shoe), zona (zone), zumbido (hum, as a noun), zurdo (left-handed).

Open any Spanish-English dictionary at the letter "z", and you'll find a lot more.