What is the ruling on sometimes abandoning the regular Sunnah prayers, and the four rak'ahs before Dhuhr and four after it, in university, even when there is ample time?

There is no blame in abandoning the Sunnah of Dhuhr, because it is not obligatory. However, it is better to maintain it because the Prophet, peace and blessings be upon him, if he did an act, he would establish it. The most beloved deeds to Allah are those that are most continuous, even if they are small. This is also due to what has been reported regarding the virtue of the four rak'ahs before Dhuhr and four after it, that they forbid their doer from Hellfire. Furthermore, supererogatory prayers compensate for deficiencies in obligatory prayers on the Day of Judgment.