Must say, gym and Zwift bores the hell out of me. Thinks about it for a mili-second, get's on bike in the 'fresh air'.
Fresh air being wind, rain, minus seven, occasional sunshine. I 'should' do weights being in my mid 50's, but...
Load bearing exercise is better at preserving bone density and muscle though, especially as you age, even press ups and pull ups will do that far better than just cycling.