جَاءَ غُلَامُ زَيْدٍ
Translation: Zayd’s servant came.
جَاءَ: past-tense verb.
غُلَامُ: nominative subject (fāʿil), marked by ḍammah, and mudāf.
زَيْدٍ: genitive mudāf ilayh, marked by kasrah.
In رَأَيْتُ غُلَامَ زَيْدٍ, ghulāma is an accusative direct object while Zaydin stays genitive. The mudāf changes case according to its sentence role; the mudāf ilayh remains genitive.