samṛddhānāṁ ca yat surāḥ

tasya-that; ayam-this; anayasya-of your ungrateful activity; asit-was; parebhyah-by others; vah-of all of you; parabhavah-the defeat; praksinebhyah-although they were weak; sva-vairibhyah-by your own enemies, who were previously defeated by you; samrddhanam-being yourselves very opulent; ca-and; yat-which; surah-O demigods.