Is the repentance of someone who repeatedly commits zina (fornication/adultery), repents, then relapses, then repents and performs Umrah, then relapses again—knowing that he feels deep remorse after each time and resolves to repent—accepted? And is that considered mockery of Allah?

Repentance and turning to Allah are obligatory upon committing a sin, and one must not persist in it, for that is destruction. Repeatedly falling into sin and then repenting is not mocking Allah; rather, it is a sign of His love and hatred of sin. Allah accepts repentance even if sins are repeated. Sincere repentance requires abstaining from the sin, regretting it, resolving not to return to it, and restoring rights to their owners if the sin pertains to the rights of others. One must hasten to repent because death can come at any moment. Allah accepts the repentance of those who do evil while knowing it is a sin, for everyone who sins is ignorant in terms of committing the disobedience, not in terms of being ignorant of its ruling.