Is it permissible to combine the intentions of the Prayer of Sunnah of Wudu', Tahiyyat al-Masjid (Greeting the Mosque), and the two Rak'ahs of Duha (forenoon) in two Rak'ahs?

There is no harm in combining the intention for two rak'ahs: the Sunnah of Wudu, greeting the mosque (Tahiyat al-Masjid), and Duha prayer. This is because the Sunnah of Wudu and greeting the mosque are not intended for their own sake, whereas Duha prayer is intended for its own sake and is specifically designated by intention.