I need to have audio out from HDMI and headphone jack simultaneously

No. You can only use one sound output:

Why can't I select HDMI audio on my Mac mini?

If you connect an HDMI display or television to a Mac mini (Mid 2010 or later), you might not be able to select the HDMI audio device (in System Preferences > Sound > Output). This can happen if you also have headphones plugged in to the computer. Unplug the headphones to be able to select HDMI audio.

Mac computers: Frequently asked questions about using HDMI

There is a little switch in the speaker jack that senses when speaker is plugged in. That switch then prevents sending audio to other outputs if the speaker is plugged in