As someone said, an interesting association belatedly realized:
1. PF: "the three conjoined lakes called Omega, Ozero, and Zero"
2. "Signs and Symbols": "I will tell you what you are doing; you are turning to the letter O instead of the zero."
While I have no doubt thought about the zeros in both works, and their relationship to death/afterlife/nothingness, I guess I hadn't specifically put the exact phrase from the short story together with PF's Ozero. The effect heightens the association with suicide and the worry of parents for the fate of their child.