First I thought the level wasn't stable at the ball pit area as sometimes the upper ball was passable and sometimes not. I tried different sequences for the balls and then realised B had to do something crucial and eventually it was a very great clean win.
@ohmytian - Thanks for playing, commenting and rating. I'll add a note in the description ref your issue.
What @Link said above. I played this last night and took me three attempts as I wasn't paying much attention to Z and B accidentally got zapped. The next two attempts? Messed up on the last ball then finally won. Thanks @Meko Guy