“‘Z’ is a letter symbolizing Nikon’s new camera brand,” Nikon says. “To emphasize this, there is a space between Z and 7/6.”
But there’s also the fact that camera models across the industry traditionally don’t contain a space in the middle (e.g. Canon 5D, Sony a9, Leica M10). Even Nikon’s latest DSLRs have names such as the D5, D850, and D7500, not the D 5, D 850, and D 7500.
Uh, good luck with that, Nikon.