Save the file 'Pipboy_MapPage.swf' present in ...\Data\interface\ (always better)

- If JPEX's Free Flash Decompiler is installed on your computer, double-clic on Pipboy_MapPage.swf.
   If not: JPEX's Free Flash Decompiler (Opensource).

- Go to script\scaleform\WorldMapHolder

- With JPEXS 8.xx, for some reason (of multiplication...), it is better to write the changes in the right window.
   So, in the "Source ActionScript" window (middle), clic on a line with a value in it. The most right-side window appears.

- Use the "Edit" button of that window to change the values.
These values are for all the Maps except Satellite World Map. That mod uses an .esp which modifies the map frame size.

FOR 8K World Map:
MIN_SCALE = 0.095;                                                (default 0.75) - This is the max Zoom-out
MAX_SCALE = 3;                                                      (default 5) - This is the max Zoom-in
START_ZOOM = 0.045;                                            (default 0.117647) - Standard Zoom height. The higher the number, the closer to the ground
TOP_PAN_GUTTER_PCT = 0.15;                                (default 0.06335414969680514) - Northern frame limit
MOUSE_WHEEL_ZOOM_SPEED = 0.015;                     (default 0.15) - The intermediary scroll heights ratio

FOR 4K World Map:
MIN_SCALE = 0.2;                                                    (default 0.75) - This is the max Zoom-out
MAX_SCALE = 5;                                                      (default 5) - This is the max Zoom-in
START_ZOOM = 0.0475;                                           (default 0.117647) - Standard Zoom height. The higher the number, the closer to the ground
TOP_PAN_GUTTER_PCT = 0.15;                                (default 0.06335414969680514) - Northern frame limit
MOUSE_WHEEL_ZOOM_SPEED = 0.02;                       (default 0.15) - The intermediary scroll heights ratio

FOR 2K World Map:
MIN_SCALE = 0.4;                                                    (default 0.75) - This is the max Zoom-out
MAX_SCALE = 4;                                                      (default 5) - This is the max Zoom-in
START_ZOOM = 0.1;                                                (default 0.117647) - Standard Zoom height. The higher the number, the closer to the ground
TOP_PAN_GUTTER_PCT = 0.15;                                (default 0.06335414969680514) - Northern frame limit
MOUSE_WHEEL_ZOOM_SPEED = 0.05;                       (default 0.15) - The intermediary scroll heights ratio

- Clic on Save (the CODE)

- Then Save the FILE in ...\Fallout 4\Data\interface\

Good to know: It is not necessary to exit and relaunch the game to load new values. Just reopen the map after the changes have been saved.
Voilà.