Double negatives exist in English, but their usage is considered grammatically improper. In Zekaiseivarsei, however, double negatives can properly be used for emphasis.

zih ame zu zist Zih and zist are both negatives, so logically they should cancel each other out, but in Zekaiseivarsei, they do not. Instead, they form a hypernegative. 

The sentence literally translates to "not I love you nothing" (or "I do not love you nothing"). In Zekaiseivarseivarsei, though, it means "I don't love you at all."

What if I mean to negate the negative? Edit

If you mean to negate the negative, simply use the NEG ya NEG construction.

dwi zi ya zi sha e sha ra (two not PARTICLE OF RELATION not one and one PARTICLE OF EQUALITY, English: two does not not equal one plus one.) This means that two equals not not one plus one, which is the same as equaling one plus one.