Why find + FFmpeg work incorrectly?

Question

fmpeg

There is a poppy on which I convert videos from mov, mkv and avi to .mp4.

find ~/Desktop/origin -name "*.mkv" -o -name "*.avi" -o -name "*.mov"  -exec ffmpeg -loglevel warning -stats -i {} -pix_fmt yuv420p -vf scale=1280:720:flags=bicubic -f mp4 -c:v h264_videotoolbox -b:v 2100k -c:a aac -b:a 128k "{} | converted.mp4" \;

As soon as I run it, it only converts the last type of file entered (now, for example, it will only convert mov). How can I fix this problem so that ffmpeg will convert all input data types?

Thank you.