Bhagavad Gita · Karma Sannyasa YogaChapter 5, Shloka 29 (5.29)

Three epithets:

1. Enjoyer — all yajnas and austerities reach Him (9.24 ahaṃ hi sarva-yajñānāṃ bhoktā).
2. Great Lord of all the worlds — the master of all.
3. Friend (suhrid) — the selfless friend of all. The third epithet turns the power of the first two into love.

Shankaracharya. Evaṃ samāhita-cittena kiṃ vijñeyam — what is to be known with a composed mind? Answer: bhoktāraṃ yajña-tapasāṃ … kartṛ-rūpeṇa devatā-rūpeṇa ca — the enjoyer of yajna and austerity, both in the form of the doer and in the form of the deity; suhṛdaṃ sarva-bhūtānāṃ … pratyupakāra-nirapekṣatayā upakāriṇam — one who does good without expecting anything in return; sarva-bhūtānāṃ hṛdayeśayaṃ sarva-karma-phalādhyakṣaṃ sarva-pratyaya-sākṣiṇaṃ māṃ nārāyaṇaṃ jñātvā — knowing Me, Narayana, who dwells in the hearts of all, presides over the fruits of all actions and witnesses all experiences — one attains śāntiṃ sarva-saṃsāroparatim — the peace that is the cessation of all samsara.

Acharya Ramanuja — karma yoga with ease. Karma-yoga-karaṇa eva sukham ṛcchati — one finds happiness in the very doing of karma yoga. Sarva-loka-maheśvaraṃ sarveṣāṃ lokeśvarāṇām api īśvaram — the Lord even of the lords of the worlds — taṃ īśvarāṇāṃ paramaṃ maheśvaram (Śvetāśvatara Up. 6.7). The main argument: māṃ … sarva-suhṛdaṃ jñātvā mad-ārādhana-rūpaḥ karma-yoga iti sukhena tatra pravartate — knowing Me as the friend of all, one engages in karma yoga happily, in the spirit of "karma yoga is My worship"; because suhṛdām ārādhanāya sarve pravartante — everyone gladly works to please a friend.

The difference: Shankara — the object to be known in meditation is Narayana, and the fruit is the cessation of samsara; Ramanuja — knowing Ishvara as friend makes karma yoga easy and joyful (which is what Ramanuja said at the end of 5.28: the suśakatā of karma yoga).