The Vedanta Sutras, commentary by Sankaracharya (SBE34), tr. by George Thibaut  at sacred-texts.com
27. If it be said that (the corporeal individuality of the gods involves) a contradiction to (sacrificial) works; we deny that, on account of the observation of the assumption (on the part of the gods) of several (forms).
If the right of the gods, and other beings superior to men, to the acquisition of knowledge is founded on the assumption of their corporeality, &c., we shall have to admit, in consequence of that corporeality, that Indra and the other gods stand in the relation of subordinate members (anga) to sacrificial acts, by means of their being present in person
just as the priests are. But this admission will lead to 'a contradiction in the sacrificial acts,' because the circumstance of the gods forming the members of sacrificial acts by means of their personal presence, is neither actually observed nor possible. For it is not possible that one and the same Indra should, at the same time, be present in person at many sacrifices.
To this we reply, that there is no such contradiction.--Why?--On account of the assumption of several (forms). For it is possible for one and the same divine Self to assume several forms at the same time.--How is that known?--From observation.--For a scriptural passage at first replies to the question how many gods there are, by the declaration that there are 'Three and three hundred, three and three thousand,' and subsequently, on the question who they are, declares 'They (the 303 and 3003) are only the various powers of them, in reality there are only thirty-three gods' (Bri. Up. III, 9, 1, 2); showing thereby that one and the same divine Self may at the same time appear in many forms. After that it proceeds to show that these thirty-three gods themselves are in reality contained in six, five, &c., and, finally, by replying to the question, 'Who is the one god?' that Breath is the one god, shows that the gods are all forms of Breath, and that Breath, therefore, can at the same time appear in many forms.--Smriti also has a similar statement, 'A Yogin, O hero of the Bharatas, may, by his power, multiply his Self in many thousand shapes, and in them walk about on the earth. In some he may enjoy the objects, in others he may undergo dire penance, and, finally, he may again retract them all, just as the sun retracts the multitude of his rays.' If such Smriti passages as the above declare that even Yogins, who have merely acquired various extraordinary powers, such as subtlety of body, and the like, may animate several bodies at the same time, how much more capable of such feats must the gods be, who naturally possess all supernatural powers. The gods thus being able to assume several shapes, a god may divide himself into many forms and enter into relation with many sacrifices at the same time, remaining all the
while unseen by others, in consequence of his power to render himself invisible.
The latter part of the Sutra may be explained in a different manner also, viz. as meaning that even beings enjoying corporeal individuality are seen to enter into mere subordinate relation to more than one action. Sometimes, indeed, one individual does not at the same time enter into subordinate relation to different actions; one Brahmana, for instance, is not at the same time entertained by many entertainers. But in other cases one individual stands in subordinate relation to many actions at the same time; one Brâhmana, for instance, may constitute the object of the reverence done to him by many persons at the same time. Similarly, it is possible that, as the sacrifice consists in the parting (on the part of the sacrificer with some offering) with a view (to some divinity), many persons may at the same time part with their respective offerings, all of them having in view one and the same individual divinity. The individuality of the gods does not, therefore, involve any contradiction in sacrificial works.