How do I play a video in the YouTube app at zero volume while simultaneously playing music in an MP3 player app? Sometimes, I love to play music at a high volume while watching text YouTube videos and muting YouTube, like what I do on PC. 

I have a Huawei phone running Android 5.0 (Lollipop).
Find an app that works similar to multiscreen on Samsung devices. I use a Samsung and it comes preloaded with multiscreen. You may find an alternative on the play store.