Ukraine is the birthplace of Russia. Today’s larger Russia expanded out of Ukraine. In the 20th Century the new Union of Soviet Socialist Republics allowed the creation of a separate Soviet Republic of Ukraine. It was during the time of the Soviet Union that Ukraine became a major manufacturer of weapon systems for the U.S.S.R. In 1991, Ukraine lead the collapse of the Soviet Union by declaring independence. Then there was the creation of the European Union (EU). Both the EU and NATO have been actively involved in ‘behind-the-scenes’ influence of the Ukrainian government, for decades now. Despite that, even today Russia and Ukraine use the same type of major weapon systems. How do you tell them apart during combat?
This T-64BV is not marked, but carries large Russian and Donbas militia flags.
Russia has obviously thought about that because their ground vehicles, along with the military ground vehicles of Donetsk Republic and Lugansk (Luhansk) Republic have been given unique operational markings. They look like Latin alphabet letters but are not. They also indicate the Area of Operation (AO); North in Kiev Oblast, or South in Donbas.
Video from the end of February 2022, Donbas-Lugansk Republic militia and their trucks, BMP-1s and 2S1 SP Guns, all marked with ‘Z’, waiting for orders to move-out:
Somewhere in Donbas.
In the Southern, Donbas area of operation (AO), Russian, Lugansk and Donetsk tracked and wheeled vehicles are marked with a ‘Z’.
Ukrainian made KrAZ armored car, in use by local Donbas forces.
Video of Russians meeting with Lugansk Republic troops, 03MAR2022:
T-64BV somewhere in Donbas.
Video report, posted on 03MAR2022, Ukrainian Ground Forces abandoned a T-64BV, Lugansk Republic forces quickly claimed it by spraying ‘Z‘ symbols on it, and working to repair it for their own use (it was one of two abandoned T-64BVs, the video also shows an abandoned BRDM-2):
Abandoned Ukrainian T-64BV, now in the hands of the Donbas militias as indicated by the ‘Z’ painted on the skirts.
In the Northern Kiev Oblast AO the vehicles are marked with a ‘V’. Video of ‘V‘ marked Russian BMPs, BRTs and T-72B3s entering the Kiev Oblast of Ukraine from Belarus, the road sign gives the location away as the Gomel (Homiel) Oblast, Belarus-Kiev Oblast, Ukraine border crossing (heading towards Chernobyl Exclusion Zone?), 03MAR2022:
When you see a Western news report about Russian activities, if they are talking about Kiev AO (Area of Operation), but the images show vehicles with ‘Z‘ on them then the images are actually from the Donbas AO.
New Cold War 2022: 
RUSSIAN T-72B3M LIVE FIRE CRIMEA!
UKRAINE ABANDONS THEIR BTR-4ES WITHOUT A FIGHT!
Vehicle I-D:
2S1, FROM COLD WAR TO UKRAINIAN BORDER CRISIS!