We review the current status of the minimal nonsupersymmetric SO(10) grand unified theory and perform a detailed next-to-leading-order analysis of the gauge unification and proton lifetime constraints on the part of its parameter space supporting a ZeV-scale color sextet scalar. This, together with a TeV-scale color octet studied in detail in a preceding work, represents one of the two minimally fine-tuned settings compatible with all the relevant consistency and phenomenology limits.
Both these scenarios can be extensively tested at the future megaton-scale proton-decay facilities. On top of that, the light octet solution can be accessible in the TeV-scale collider searches.