What causes the long vowel in «مَأْكُولٍ»?

Al-Fīl and Quraysh: Applied Iẓhār, Ikhfāʾ, Idghām, Madd and Waqf

Mīm after mīm
A madd wāw after ḍammah
A līn yāʾ after fatḥah
Hamzah after tanwīn