Besides wāw → yāʾ, what occurs in دُلُوٌّ → دِلِيٌّ?

Miscellaneous Morphological Explanations: Eight Rules for Wāw, Yāʾ, Alif and Hamzah

• Add nūn by removing tanwīn
• Keep both wāws unchanged
• Replace the root
• Kasra on the preceding letter