https://zandronum.com/download

Use option

Archive (Core only)
or
Archive for 64-bit (Core only)

Unzip and copy content into dosbox folder of Doom

C:\Program Files (x86)\Steam\steamapps\common\Ultimate Doom\dosbox

Copy wads from base folder into dosbox folder

Path of base folder C:\Program Files (x86)\Steam\steamapps\common\Ultimate Doom\base
Path of dosbox folder C:\Program Files (x86)\Steam\steamapps\common\Ultimate Doom\dosbox

Just delete dosbox.exe file and rename file zandronum.exe you add earlier, into dosbox.exe

Drag and drop mod of your choice onto dosbox (Zandronum) icon. Exit after load. This operation should make you a .ini file. in dosbox folder.

Click edit on .ini file. Make your way to section Global.Autoload you have there a quick info.

# Wad files to automatically load depending on the game and IWAD you are
# playing. You may have have files that are loaded for all similar IWADs
# (the game) and files that are only loaded for particular IWADs. For example,
# any files listed under Doom.Autoload will be loaded for any version of Doom,
# but files listed under Doom2.Autoload will only load when you are
# playing Doom 2.

You must put full path with command 'Path=' to mod below [Doom.Autoload] or/and [Doom1.Autoload] etc.

For me it's like this

[Doom.Autoload]
Path=C:\Program Files (x86)\Steam\steamapps\common\Ultimate Doom\dosbox\brutalv22test4.pk3

Run Doom via dosbox option choose your wad, and enjoy. You can make screenshots and gametime will be added.