It's highly unlikely but you can't really blame Zelenskiy for trying to paint this picture.Why? A 1/6 loss ration is far from unbelivable when you consider the meat grinder tactics the Russians have been using.
Meduza & Mediazona estimate Russian losses (deaths specifically) up to the end of 2023 at around 75k (between 66 to 88k). Those numbers are based on the excess mortality data. It's important to note that those numbers don't include deaths of those who were fighting as a part of the so-called Lughansk & Donetsk Peoples Republics forces (but it includes Wagner and other PMC).
Their study is way more detailed than the English article suggests but I don't think that they've translated it in full.