Unfortunately, I feel the new meter is probably correct. I echo RChung above.

Plain and simple, when I ride Zwift with a smart trainer I see all manner of odd stuff from riders on virtual Zwift power. Either reading way way too high like flying along at 500w for an hour at a time OR the opposite, so low the person is barely moving 1mph but spinning 100rpm or so wondering what is wrong.

For now, I'd trust the Garmins and eat some humble pie.

My 1:1 on this issue is that I used a spin bike in our work gym for a couple years at lunch time and sometimes even after work. It had a Powertab hub on the flywheel. It was a Cycleops I think. I did my intervals on it, even tried out Zwift by just changing the ERG power as I went along and "pretended".

That thing thought at the time I had done 20min at around 300w. I could NEVER get close to that outdoors on the bike, even for like 8min.

Well, it wound up it was a super generous meter on that bike. I bought a Kickr and that and my Quarq and even my junkie Stages all read within 15w of each other at that power. All of them reading lower. So.........I ate my humble pie and got on with it.

Just be consistent now to use the new pedals. If you buy a smart trainer, and it seems a bit too "off" from your pedals........tell Zwift to use the pedals instead for the power. Then you always are the same.

If you REALLY care, ask to ride somebody's bike on a fluid trainer that has a known good meter. Even then this comparison doesn't tell you much as theirs might be wrong. But if you get a third reading proving the same thing.......you've got a trend going. When my Quarq, my Stages, and my Kickr all read lower (based on workout results) from that spin bike........I knew it had to be the spin bike reading high.

Enjoy! Don't despair. Just reset the mind and go from there.