as you know screen cast is missing from flyme os
instead theres the old DLNA setting that it doesent even work in settings>more>wireless display
well thankfully  the cast featury is still into the system hidden
thats how to access it

1.download an app that can browse activities like QuickShosrtcutMaker
2.on activities tab go to settings
3.expand settings and look for wireless display
4.the activity is "com.android.settings.Settings$WifidisplaySettingsActivity"
5.open it
6.you can try it and preview the cast feature
7.you can change the label (name of shortcut)
8.you can change the icon of the shortcut
9.hit create
10.a new "screen cast" icon apears on your home screen

its a shame to MEIZU that such a core android feature is not fully implemented in to the OS