This is my first post, please be kind

I'm experimenting with the imagemagick convert and mogrify commands. I have a lot of png images that I would like to:
set "black" to being transparent
crop the image so that it is 60x108+124+40
and then resize to 25% of the original size.
I've tried the command: mogrify *.png -alpha set -resize 25% -transparent black -crop 60x108+124+40
but other than change the image size from 26.8 kb to 17.1 kb, it doesn't seem to do anything.
Even when I re-order the commands into the sequence I'd like them carried out:
mogrify *.png -alpha set -transparent black -crop 60x108+124+40 -resize 25%
- nothing seems to happen.
Can anyone help?
Many thanks!
Best wishes
Paul