Depends on what sort of defense and hardening the CCP, Iran, and their partners put around it.
I wouldn't be shocked if one of the parties bought a few S-400s to stick around the pipeline's path, and putting it below ground secures it against most man portable weapons that could damage it.
It's funny that you say Zachowon is overstating the difficulty, then you're pretty much going here and doing the same thing.
First off, Russian anti-air hardware hasn't shown very dependable ability to protect as well as they claim in ME skirmishes of late.
Second off, every defense platform you put along that oil pipeline isn't protecting something else.
Third off, standing US doctrine is to take out the air defenses, then the target(s) afterwards, so odds are you'd just force the US to use a larger strike package, then you're down both the pipeline,
and the AA platforms.
Fourth off, putting pipeline underground is
massively more expensive than building it across the surface. It also makes it harder to access for repairs. Putting it deep enough that standard bunker-buster rounds can't break it is getting into orders of magnitude more expensive.
Fifth off, every hour that pipeline is down for repairs, it's not pumping oil.
Sixth off, once the US establishes local air supremacy, they don't just have to blow up one chunk of the pipeline, they can strafe the merry hell out of dozens of kilometers of the thing, meaning you'll need weeks to
months to repair it, and nothing is stopping the US Air Force/Navy Air Corps from just doing it again then.
Defending stationary targets from an enemy who has aerospace superiority is more or less impossible in the modern day. The only real protection is the enemy not knowing where the target is, and with a project the size of a pipeline, you just cannot do that in this day of satellite imagery.
The only,
only way China could secure a supply of oil during a war, is if it's coming from within their own borders,
and they massively fortify the area,
and they have a way of blocking attacks from Stealth Bombers that they've managed to keep secret thus far,
and they have an ABM shield that can stop us from lobbing conventional warheads at it until it breaks.
Bluntly put, it's the next best thing to militarily impossible for them to pull that off. Their
only hope for victory is political, not military.