In plain words
Among the Rudras I am Shankara; among yakshas and rakshasas I am Kubera; among the Vasus I am fire; among mountains I am Meru.
Word for word
Among the Rudras I am Śaṅkara, and the lord of wealth among the yakṣas and rākṣasas; among the Vasus I am fire, and Meru among the peaked mountains [am] I.
The commentators
Bhagavadgītābhāṣyam· bhāṣya
रुद्राणाम् एकादशानां शङ्करश्च अस्मि । वित्तेशः कुबेरः यक्षरक्षसां यक्षाणां रक्षसां च । वसूनाम् अष्टानां पावकश्च अस्मि अग्निः । मेरुः शिखरिणां शिखरवताम् अहम् ॥ २३ ॥
In plain words
Among the Rudras, who are eleven, I am Śaṅkara. "Lord of wealth" means Kubera, lord of the Yakṣas and Rakṣases — that is, of the Yakṣas and of the Rakṣases both. Among the Vasus, who are eight, I am the purifier: Agni. And among the peaked ones — the mountains that carry summits — I am Meru.
Close to the Sanskrit
Of the Rudras, of the eleven, I am Śaṅkara. The lord of wealth — Kubera — of the Yakṣas-and-Rakṣases, that is, of the Yakṣas and of the Rakṣases. Of the Vasus, of the eight, I am the purifier, that is, Agni. Of the peaked ones — of those possessing peaks — I am Meru.