Hi Kevin. I get that you are frustrated that your real world isn’t your Zwift world with the result you are seeing different speeds but it doesn’t matter. I’m not technical enough to explain why but just go with the feel (i.e. the hills are harder) and you will get so much from Zwift.
Remember it’s the same for all of us and if you and I rode together on a real course and on a Zwift virtual course I’m willing to bet I would feel just as tired keeping up with you in both. That’s of course if I could keep up with you, which is another point why Zwift speed isn’t the same.
I think it delivers more; if in the real world I ride 100% and you rode say only 80% but were much fitter than me I’d be beaten every time. In Zwift it would be the reverse. Now when both of us give 100% then it gets real fun and who cares it the “speed” shows 1 or 100 it will be all about which of us get the line first and that applies to both worlds.
One of the problems for Zwift is that have done such a good job making Zwift seem real that many people expect more than Zwift can deliver, see lots of discussions about racing and cheating.
Under controlled conditions it is possible to use Zwift for very real competition but until everything can be certified there would be nothing stopping me for example using an eBike and beating
One of the real world rides I do I looked at the KoM time (mine placed 1000 ish BTW) I wondered what it would take to beat it so rode on my motorbike and I couldn’t get the KOM time in Strava. The result of that was I gave up worrying about if the stats were real or not. Instead I use the stats from both to monitor my personal gains (or loss), but what I don’t do is compare Zwift to Strava.
Hope that helps, and just aim for four in Zwift rather and three knowing that virtual or real world you are going faster.