Frame Challenge: You would not want to destroy the windmills anyway
There is no good reason to take out the power plant permanently. If you are already doing a combined offensive in a modern context as the OP dictates, then the invasion will either be won or lost in the time it takes them to get the power back online if you just hit the control center. The whole point of a combined and coordinated offensive like this is to hit everything of importance so fast that the targeted nation loses its ability to coordinate a defense. Making sure those assets stay lost is not important since your ground forces are expected to be entering relevant theater of operations within the week anyway.
So, as a commander you need to ask yourself if it is more important to take out the powerplant permanently or with fewer assets, and I guarantee that this is a situation where using fewer assets is more important. If you can commit 1 plane to knocking out the control center or 40 planes to leveling all of the windmills, then that is 39 other targets that are not being hit during your pivotal first offensive. Even if you go with the B-52 cluster smart bomb scenario or a smaller formation of planes using autocannons, there are going be big trade-offs. While those attacks use fewer planes, it still means taking specialized planes off the board and using up a lot of specialized ordinance which could be better utilized for attacking other targets that need those specialized planes like enemy battlements and tank formations.
The other reason you don't want to hit the windmills directly is because once you invade the country, you need to control it. Permanent damage to the enemy's infrastructure will result in being unable to re-establish a working economy once the hostile regime is taken out. If your attack destroys the economy, then those people who lost their jobs are more likely to take an active role in resisting your occupation, but if power is only down for a week, then people still have their jobs and can go back to caring about providing for their families as soon as the shooting is over. So, when you look at it from this perspective, it becomes clear that attacking the windmills directly is not only inefficient, but a worse actual end-goal given what you are trying to achieve.