Part with marking code "ZO" "607"
Could it  be ZQ? From what I can see the pinout looks like it could match.

"MIC94165YCS - ZQ - 1.5mm × 1mm 6-Ball WLCSP" 
http://static6.arrow.com/aropdfconversion/49e0c46145f1e0fbafdc3eb2279f6f3a5b83b03c/141mic9416x.pdf