I have been running on the treadmills at my gym and hooking it to Zwift using the Zwift run pod.
Stupid question time but my aim is to always cover whatever distance in the shortest time, so I have been picking routes with minimal elevation.
Does the elevation on the course make much difference to the time it takes to cover a distance.
Obviously when cycling it makes a massive difference.
Zwift does not modify the speed input based on course elevation for a treadmill/run-pod. Unless you are on a treadmill that matches Zwift elevation profiles, such as the Wahoo Kickr Run, or using a 3rd party app to set the elevation (QZ is one such app), then your treadmill elevation setting is the only thing that will slow you down.
Nice one. I didn’t think it did, doesn’t matter which course I pick then. Excellent.
Pick the steepest ones if you want to troll cyclists by jogging past them 
I had a couple of riders call me out for that, as I paced them up The Grade, sadly for them I was matching incline using QZ (I paid for it at the top, but it’s always worth it)