Akbari et al.'s zero-sum 6-flow conjecture

Let $G$ be a graph. A zero-sum $k$-flow of $G$ is an edge labeling with labels in $\{\pm1,\ldots,\pm(k-1)\}$ such that the sum of the labels on all edges incident with every vertex is zero. Zero-sum 6-flow conjecture. If $G$ admits a zero-sum flow, then $G$ admits a zero-sum $6$-flow. This conjecture concerns the existence of bounded integer edge labelings satisfying the zero-sum condition at every vertex. The source gives no resolution, so its current status is left open.