Equality of Lord Shiva and Lord Vishnu's equality are shown not one time but many times in Mahabharata
Tezz reply is also very good! and I like that
let's continue :—
Vaisampayana continued,
"Phalguna then beheld him--
Mahadeva--that god of blazing
splendour-that wielder of the
Pinaka-that one who had his abode
on the mountains (of Kailasa)--
accompanied by Uma. Bending
down on his knee and bowing with
his head, that conqueror of hostile
cities-the son of Pritha worshipped
Hara and inclined him to grace.
And Arjuna said, 'O Kapardin, O
chief of all gods, O destroyer of the
eyes of Bhaga, O god of gods, O
Mahadeva, O thou of blue throat, O
thou of matted locks, I know thee
as the Cause of all causes. O thou
of three eyes, O lord of all! Thou
art the refuge of all the gods! This
universe hath sprung from thee.
Thou art incapable of being
vanquished by the three worlds of
the celestials, the Asuras, and
men. Thou art Siva in the form of
Vishnu, and Vishnu in the form of
Siva. Thou destroyedest of old the
great sacrifice of Daksha. O Hari, O
Rudra, I bow to thee. Thou hast an
eye on thy forehead. O Sarva, O
thou that rainest objects of desire,
O bearer of the trident, O wielder
of the Pinaka, O Surya, O thou of
pure body, O Creator of all, I bow
to thee.
—— The Mahabharata, Book 3:
Vana Parva: Kairata Parva: Section
XXXIX
"Sanjaya said, 'Then Partha, with a
cheerful soul and joined hands and
eyes expanded (in wonder), gazed
at the god having the bull for his
mark and who was the receptacle
of every energy. And he beheld the
offerings he made every night to
Vasudeva lying by the side of the
Three-eyed deity. The son of
Pandu then, mentally worshiping
both Krishna and Sarva, said unto
the latter, 'I desire (to obtain) the
celestial weapon.' Hearing these
words of Partha desiring the boon
he sought, god Siva smilingly said
unto Vasudeva and Arjuna,
'Welcome to you, ye foremost of
men! I know the wish cherished by
you, and the business for which
you have come here. I will give you
what you wish.
—— The Mahabharata, Book 7:
Drona Parva: Abhimanyu-badha
Parva: Section LXXXI
You can see that there is clearly
written that Arjuna got all the
offerings in right side of Rudra that
he made to krishna every night.
Vishnu and Agni and Soma became
(as already said) the arrow. The
universe is said to consist of Agni
and Soma. The universe is similarly
said to consist of Vishnu. Vishnu
is, again, the Soul of the holy
Bhava of immeasurable energy.
For this the touch of that bow-
string became unbearable to the
Asuras.
—— The Mahabharata, Book 8:
Karna Parva: Section 34
Here vishnu is rudra's soul.
O son of Pandu, Rudra should be
known to have always Narayana for
his Soul. If that deity of deities,
viz., Maheswara, be worshipped,
then O Partha, is the puissant
Narayana also worshiped. I am
the Soul, O son of Pandu, of all
the worlds, of all the universe.
Rudra, again, is my Soul. It is for
this that I always adore him.
——The Mahabharata, Book 12:
Santi Parva: Section CCCXLII
Here Rudra is Vishnu's soul and
Vishnu is Rudra's soul.
but if you want it on a larger scale just go on my blog:—
Equality of Lord Rudra and Lord Vishnu in
Mahabharata
http://shivaandvishnu.blogspot.in/2017/09/equality-of-lord-rudra-and-lord-vishnu.html?m=1