ffmpeg audio video separate files 1 command
Daisychain the commands, so

ffmpeg -ss 04:53 -i ./07.mkv -t 3 -c:v libx264 -crf 18 -filter:v "setpts=PTS-STARTPTS, crop=960:720, scale=480:360" -an -sws_flags lanczos -fflags +genpts 07-alexFlex.mp4 -ss 04:53 -i ./07.mkv -t 3 07-alexFlex.mp3