I'm not sure how you have ended up with a ZIP file from GC.
If you go into the ride on Garmin Connect, and click on the small cog-wheel on the top right ( tool tip says "more...")
then you have the option to export as GPX.
That always gives me a GPX, not ZIP.
Anyways, if you've managed to get the ride onto GC, then it's on your Edge.
You should be able to plug it into the PC, and in Strava you should be able to click the Plus icon and select 'Upload Activity'.
Then, choose the FILE option on the left hand toolbar.
Click 'Choose Files', and navigate to your Edge device, and go into the \Garmin\Activities folder, and select the correct FIT file and upload it.