He has repented from zina; does the hadd punishment have to be carried out on him?

Undoubtedly zina is a major sin, and among the means that
lead to it are nakedness of women, mixing of men with non-mahram women, the
decline in morals and the corruptness of the environment in general. If you
committed zina because of being away from your wife and mixing with evil and
corrupt people, then you regretted your sin and repented to Allaah
sincerely, then we hope that Allaah will accept your repentance and forgive
your sin, because Allaah says (interpretation of the meaning): 

“And those who invoke
not any other ilâh (god) along with Allaah, nor kill such person as Allaah
has forbidden, except for just cause, nor commit illegal sexual intercourse and whoever does this shall receive the punishment.

69. The torment will be doubled to him on the Day of
Resurrection, and he will abide therein in disgrace;

70. Except those who repent and believe (in Islamic
Monotheism), and do righteous deeds; for those, Allaah will change their
sins into good deeds, and Allaah is Oft‑Forgiving, Most Merciful”

[al-Furqaan 25:68-70]

And it was narrated from ‘Ubaadah ibn al-Saamit (may Allaah
be pleased with him), in the hadeeth about the women’s oath of allegiance,
that the Prophet (peace and blessings of Allaah be upon him) said:
“Whoever among you is faithful (to this pledge) his reward will be with
Allaah, and whoever does any of these things and is punished, his punishment
will be an expiation for him, and whoever does any of these things but
Allaah conceals him, then it is up to Allaah: if He wills He will punish him
and if He wills He will forgive him.” 

But you have to flee from
this corrupt environment that tempts you to sin and seek to earn a living in
another country that is less evil, so as to protect your religious
commitment. The earth of Allaah is spacious and no one will ever be without
a land where he can earn a living and acquire the provision that Allaah has
decreed for him. And whoever fears Allaah, He will make a way for him to get
out (from every difficulty) And He will provide him from (sources) he never
could imagine.