>>15797384 (lb)

On March 2, the Russian Ministry of Defense revealed a more straightforward answer, at least for Z and V, as reported by pro-Ukraine site Unian.

Z stands for the Russian words “За победу” (Za Pobedu), meaning “for victory.” “З” is the Cyrillic equivalent of the Latin “z.”

V — written as “в” in Cyrillic — stands refers to the “v” in the phrases “Сила в правде” (Sila v pravde) and “Задача будет выполнена” (Zadacha budet vypolnena) — “in truth lies power” and “the mission will be completed,” according to the defense ministry.

It appears there is still no official explanation for the meaning of “O.”

https://www.visiontimes.com/2022/03/03/meaning-of-z-and-v-painted-on-russian-tanks-in-ukraine.html