How can the seemingly contradictory prophetic hadiths be reconciled with some verses of the Holy Quran, such as the hadith "Whoever changes his religion, kill him" versus the verse "Are you then to compel people until they become believers"? And what about other examples related to polygyny and the shortening of prayers during travel?

What has been authentically transmitted from the Prophet, peace and blessings be upon him, from the Sunnah does not contradict the Holy Qur'an, for both are revelations from Allah Almighty.

The Sunnah is the interpreter and elaborator of Allah's intent in His Book, and the Qur'an cannot be understood in isolation from it. Scholars have affirmed that the Qur'an is more in need of the Sunnah than the Sunnah is of the Qur'an, and that the Sunnah is a judge over the Qur'an, which is indicated by legal texts.

Preserving the Qur'an from distortion necessitates preserving the Sunnah, because it explains it.

There is no contradiction between the verses of the Qur'an and the texts of the Sunnah. The Sunnah clarifies the generalities of the Qur'an, specifies its universals, restricts its absolutes, and elucidates its complexities. The examples mentioned in the question do not represent a true contradiction; rather, they are situations that require a precise understanding of the Sunnah and how it interprets the Qur'an.

The alleged contradiction between the Qur'an and the Sunnah arises from a failure to acknowledge the authority of the Sunnah or from ignorance of how to reconcile between them.