They have more than a million men under arms, while Zelenskyy is down to dragging 40 year olds off the street."
Estimates I've seen of total Ukrainian armed forces, including police, are circa one million.
Estimates of Ukraine's maximum potential military manpower population are something like 20 million.
However, if we compare to Israel, out of 9 million total population, Israel has about 3 million of military age, of whom roughly 1 million serve in some capacity, especially reserves.
For Ukraine, that would mean possibly 33 million total population, around 10+ million of normal military age with potentially 3+ million serving in some capacity.
Estimates of Russian forces in and around Ukraine are in the 300,000 range.
All that said, what seems certain is that the dictator Vlad the Invader can sustain "Meat Wave" assault losses in the range of 1,000 per day, while more democratic Ukrainians obviously cannot.