I'm not saying that the Russian army will not be able to defeat Ukrainian. I told you about the loss of the price, which will provide it to her. Russian VKS and navy a year hammering Syrian rebels, who have the most formidable air defense weapon is Chinese MANPADS and S-60.
American coalition (60 countries) has hammered Syrian rebels for a 4 years and results are more modest than Russian VKS made in 2 weeks. What does it say? Nothing.
1 - ISIS is not a classical state (Ukraine is) and cannot be crippled and destroyed by hitting just limited amount of crucial targets (Ukraine can be killed by destruction of some 50 crucial targets).
ISIS is a distributed, P2P network organization without political and subordination vertical structure.
So if you have to destroy it, you must destroy it all, target by target, like Heracles has killing the Hydra - smash the head - burn the neck, smash a tentacle - burn the wound. If you will not do this, such strcture will renew destructed part again (especially with Western constant support). VKS task is to kill ISIS supplies and personnell faster than West can renew it, and VKS is successfull in it.
What a soldier (or even officer!!) you are, if you don't know and realize such an elementary things in your structural analysis???
2 - Russian goals in Syria was not to destroy ISIS in any cost, but to gain political score and dividents in global struggle + get airforce and navy bases in Mediterranean.
Russians don't plan to defeat ISIS instead of Syrians, but support Syrians to allow them to get strong and defeat ISIS themselves with Russian support. Making strong allies is more valuable thing than just shake muscles.
3 - Ukraine is not ISIS. It is a classical state (a failed state, actually), so it can be killed by state pillars (key targets) destruction. In 21-st century you don't need to control each meter of soil to capture the country.
You need to hold a key points. Then you can whatever you want.
This is easy to do in Ukrainian case while ukrainian army is weak, poorly armed and equipped, and THE MOST IMPORTANT - it has no viable AF, AD, recon, communications, targetting and ESM/ECM units to show real resistance to an adequate foe. All Ukainian key targets can be defeated with some 250 CMs/BMs in the first 2 hours of conflict. The rest (including AD and AF) will be killed in the next two from the safe distance, while ukroarmy is blind.
What to say if our "army" cannot beat even coal miners and taxi drivers in Donbass militia, not talking about ANY real army (Russian army is not reachable for them at all).
In Ukrainian case there will be no fanatic resistance like ISIS can, so capturing of Ukraine will not cause any significant losses.