My android phone speaker is quite loud usually but in Zoom really low?

[Jibun-no-Kage]

Android phone speaker is quite loud usually, for example YouTube, MAX, Google, etc., but in Zoom really low?  I see many topics in this forum and comments via Google search, where Zoom never really answers the question.  And, if you say I need to turn up the volume on my phone... it is already at the maximum output and it is only about 50 percent of maximum in Zoom, explicitly in Zoom is the issue.  The very second I move to any other app on my phone, it is very loud again, compared to Zoom.  Surely Zoom can address this issue proactively?