Nice pics!!!
Totally right, digital zoom use software to zoom in and quality will be affected. For quality choose only optical zoom.
You may edit after and zoom in using Photoshop or other, and will get similar result and maybe with few edits a better quality pic.
I read that's the case, digital zoom is better during processing than before the processing. So, I guess, I'll just use optical zoom from now on especially for shooting the moon to get better clarity of it.