feel ashamed
慚 centers on the feeling of shame or embarrassment, especially a deep personal sense of having done wrong.
慚 combines the heart radical 忄 with 斬, which likely contributes the sound and may suggest cutting or severing one's honor, leading to shame.
The heart 忄 beside 斬 (cut) suggests a heart cut by shame: feeling deeply ashamed.
For ザン, imagine feeling so ashamed you want to vanish: zan sounds like the start of 'vanish' without the 'v', and the shame makes you want to disappear.