Is the repentance of one who has committed the abomination of Zina accepted, when he is now remorseful, regular in prayer, and a reader of the Book of Allah, after having abandoned the bad company that led him to that sin?

Congratulations to you for your regret and your fear of punishment and your interest in righteous deeds, for these are among the greatest means of repentance. Regret is repentance, and abandoning bad company and moving to the company of good people, and increasing righteous deeds after sincere repentance are among the greatest causes of Allah's mercy and forgiveness. Continue to acquire the means of guidance and uprightness, and be keen on marriage or persist in voluntary fasting and lowering your gaze, and fill your time with righteous deeds, beneficial knowledge, and the prescribed remembrances. Have a good opinion of Allah and supplicate frequently, and beware of thinking about suicide, and cover yourself and do not tell anyone what happened.