Recompressing many huge MOV files
My earlier answer still holds in general. Additional advice I can provide is to try higher CRF values and use the veryslow preset.

ffmpeg -i input.mov -c:v libx264 -crf 23 -preset veryslow -c:a copy -c:d copy -map 0 compressed.mov


You can also mimic a constrained quality mode by setting

ffmpeg -i input.mov -c:v libx264 -crf 21 -preset veryslow -maxrate 5M -bufsize 10M -c:a copy -c:d copy -map 0 compressed.mov