Xander99 Ezoic will show Adsense ads via Mediation when they bid the highest - by using Ezoic you are not excluding your Adsense ads from generating you revenue - what you are doing is only showing Adsense ads in circumstances where they bid the most. Where you have not earned mediation revenue, it's because Ezoic network partners have bid higher than Adsense, so if you were to turn off Ezoic, you would have earned less on all those days where Mediation earnings are not showing in your dashboard.
You would also have lost the AI optimization Ezoic applies to your website to adapt the ad sizes, types, and number of ads on the page to suit each user's preference, which improves user experience, as well as Ezoic's unique ad types, for example our universal player, which is earning many publishers over 50% more at the moment. (If you haven't had chance to check that out yet here's some more info you may be interested in: https://community.ezoic.com/d/30916-maximize-your-earnings-introducing-the-universal-video-player ).
You won't be able to compare the root domain earnings to the sub domain as there's many factors that affect that e.g such as the content, so it wouldn't be comparing apples to apples. It doesn't look like your sub domains are using Ezoic right now though - if you want to try Ezoic on your sub domains let us know the URLs for these and our team can review them.