Usefull for AZERTY keyboard:

1. In game options, bind MOVE CAMERA UP to U key (as Z is forbidden), then quit the game.
2. Go to folder C:\Users\[You]\AppData\LocalLow\Snapshot Games Inc\Phoenix Point\GOG\Saves,
3. open/edit Bindings.jopt file with Notepad++
4. Go arround the two lines 280, and 295: in both [ "Name": "u", ] change 'u' to 'z'
5. Save the file and go launch the game to verifye in options that MOVE CAMERA UP has now Z key.

And how to reverse the mouse wheel zoom?

It’s not possible in the game settings, but if you have a mouse that comes with user profile settings, you could set it up there.