Zodiac is the Resurgence map. Rally Point is a mode on Zodiac; three of the camos only count there.
You'll know it worked when the screen shows Secret Challenge Completed with the reward icon above it.
Zodiac Railway unlocks just by playing 5 matches, so in Easiest first it sits on its own at the bottom.
Most of these come from players' posts in the first days of the season. Where a post doesn't say something for sure, the card tells you.
How it works
Tap a number in the bar (or Show on the map on a card) to show only that challenge on the map. Tap it again, or Show all, to see every one.
Tap a numbered pin to see that spot's picture in its card, then mark it found. Each card's Map spots list has the same ticks.
Scroll, pinch or use + / − to zoom. Dashed pins and "approx" spots are close but not exact; the rest are placed from Expel's own minimap.
Steps go one at a time: use the arrows (or swipe, or the arrow keys). All steps shows them stacked.
Mark done turns a card green and moves it to Done at the bottom. Undo puts it back. Green numbers in the bar are done.
Easiest first puts quick solo ones first; Recommended starts the background ones, then one route through a Rally Point match. The numbers follow the order you pick.