YOU SAID:
The zipper on my pencil case broke.
INTO JAPANESE
私の筆箱のジッパーが壊れた。
BACK INTO ENGLISH
The zipper of my pencil case broke.
INTO JAPANESE
私の筆箱のジッパーが壊れた。
BACK INTO ENGLISH
The zipper of my pencil case broke.
That didn't even make that much sense in English.