@stpijb
Those .zip are all world files, they can't be used a schematic.
But there are several ways to change it into a schematic file:
1. Load it as a single player world
and use the schematic mod
to save part of the map
into a
.schematic file
2. Load the world file into some
other apps like MCEdit, which can
be used to transform a part of the world
into a
.schematic file
If you're lazy to do things above, you can go visit https://www.minecraft-schematics.com/
It's where those
schematic users upload their projects,
most of them can be download as
.schematic
NOTE: Only tag will notify the user, say my name won't.
(tag with @<user>)</user>
Discord: Untrustable#8110