This is now my second run that is tacked on a bunch of time at the end. Like I get it, I’m slow… But I’m trying to get better and this is really messing with my confidence. Lol
Today zwift said my 5k took 46 minutes… Strava 36. And it was a 36 minute run.
Both times it’s happened I make sure to hit end run at the end.
Any ideas what’s happening?
Zwift’s time is the total time you were “in-game” (ie the second you spawn on the side of the road until you hit end). So if you were going a group run or race and sat in the pens for 10 minutes before starting that is the difference.
Strava and Garmin (and most other 3rd party sites) use moving time for their display, so the time you just sit idle not running won’t show up on their sites.
But for the 5k I did this morning it showed that I did 3.14 miles in time of 43 (not 46) minutes. First mile in 12 min/mile, 2nd in 11:54/mi, 3rd 11:16/mi, and the .14 in 21:52/mi… So I don’t think that’s it. Like I was actually running before the 5k not just standing there so if it had included that it would have shown higher mileage than 3.14 Sorry to mix kms and miles… 
Just looked at your activity and it was the Eric Min group run so I assume you logged into Zwift, joined the group event, and were waiting in the pens before the start of the run. Like I said above Zwift counts that time just sitting in the pens waiting to start as part of the activity time whereas Strava uses “moving time” so the minutes you weren’t virtually running and just standing still are removed from the time displayed on Strava