So, as you can see this IS a 3.0si but not a 3.0si Sport - it's an SE spec 3.0si.
I don't know what kind of driving you want to do in your Zed and what kind of person you are but for what it's worth, the SE has a slightly softer suspension set up and wider, more capacious seats, making it, for some, a preferred ride but still a very capable Zed - same 265bhp engine.
The 3.0si can be difficult to source - I had to wait many months to find a Sport version at my price point but eventually was surprised to find an Authorised Used Car from BMW (so do keep checking out their web site). Consequently, prices can be strong and you may have to make a compromise on preferred colour and spec (as I did).
Most people seem enamoured by the 'Sport' spec and this might effect the eventual value?
Good luck with your search - you will be well pleased by your Zed but if you are considering an ///M and can face what are increasingly specialised high purchase costs and then the running costs and you intend to use it at weekends and for fun, then why not go straight to the ///M? I did 13000 miles + in my Zed last year despite it being a second car and most of the driving being for fun - not certain I could fund that annual mileage in an ///M. If you are buying a daily Zed, then a 3.0si makes sense as it can be cheaper to run. Worth checking out the recent posts on running costs of an ///M - interesting reading.