What happens to tanwīn in linked «هُمَزَةٍ لُمَزَةٍ»?

Al-Māʿūn and Al-Humazah: Applied Assimilation, Concealment, Madd and Hāʾ Rules

• Ikhfāʾ with ghunnah
• Clear mīm
• Necessary madd
• Assimilation into lām without ghunnah