With mouse and keyboard UI elements in the build interface are VERY clickable.
When trying to place a "city zone" item down when the interface is over the "rural zone" a player will likely be enticed to click the item they want only to have their mouse leave the "city zone" and have their options disappear.
I suspect this may confuse players even with time in the game since the UI communicates a workflow that says, "The thing you want is at the top of this list so just click it" and this interaction may confuse and cause the player to move their character further and further into the space they want to work in.
It might be good to have the zone default to the one the player is standing on. I only have my experience to speak to here but my gut tells me most players are likely to stand where they want to build and this may make narrowing choices down. It would also be helpful to provide some indication that the player is in that specific zone perhaps with a label that allows them to change the zone they're working in.
This is a kind of a nitpick... It seems like it may cause more problems than it solves. Especially with players using a controller. So I'm unsure if this feedback is actually actionable.