cero a la izquierda

a person of little or no consequence; a nobody; a nonentity

“En apariencias, el Presidente de la República está revestido de poderes casi dictatoriales; pero, constitucionalmente hablando, es un cero a la izquierda.” — Apparently, the President of the Republic [of Chile] holds almost dictatorial powers; but, constitutionally speaking, he is of little consequence.

Literally, “zero to the left”. The idiomatic meaning is presumably from the mathematical sense of the term, since any leading zeroes to the left of a number have no effect on the number's value. Compare Portuguese zero à esquerda.