You don't need to pre-zoom your work for PJ, the site has zoom buttons underneath every submission. Uploading at 1x lets the viewer decide how big to view your work, which makes it easier to give feedback.
Since your entire piece fits as the preview image at 1x, you don't need to upload a detail file at all. That feature is for larger works that don't fit in the 100x100 preview image limit.
Your colours are very low-contrast, so they're barely visible without zooming in a lot. When adding colours, make sure they pull their weight! If they're hard to see without zooming in a lot, then they're not helping your piece and may as well not be there.
Thank you for your feedback! I've only been doing pixel art for a week and have just joined this community, so your advice is very welcome :)