Ze/zir neopronouns are gender neutral pronouns and can be used by anyone regardless of gender identity or expression. Ze is pronounced the same way as xe. It was likely based on the German plural 3rd person pronoun sie.
||Ze||Ze went to the store|
||Zir||I met zir today|
||Zir||Ze walked zir dog today|
||Zirs||If I need a phone my friend will let me borrow zirs|
||Zirself||Ze had to drive zirself to school|
The first known case of ze being used is in 1997, by Richard Creel, who proposed ze/zer/mer (reflexive form is not recorded).
Another version was possibly independently created by Kate Bornstein in the 1998 book My Gender Workbook. This version uses ze (sometimes zie or sie) and hir. The most popular variation of these pronouns are based on this version and were created in 2013.