Answered by Shaykh Abu Usamah
Zayd is traveling and the time for Isha comes in. Zayd goes in the Masjid , sees a Jamaa’ah, and joins it. After the Salah is finished , Zayd realises that the the Jama’ah were non-Hanafis praying delayed Maghrib (takheer). after that they make Isha.
What is the Status of this 3 Rakah prayer Zayd made with the Jama’ah? (Zayd had already prayed Maghrib on its time). Is it considered a Nafl? Are the first two Rakaats considered Zayd’s Isha and the last Raka a Nafl? Does Zayd still have to make his Isha?
(this kind of situation is faced by a lot of people while traveling in Saudi Arabia, as one goes into a Masjid for , say Zuhr (at Zuhr Time), and joins the Jama’ah, only to find out later on that they had already finished Zuhr and were praying Asr (Taqdeem). Thus leaves a lot of Hanafis confused, whether they have to repeat thier Salah or not.)
Also, I am assuming there is no concept of Jama (combining prayers) in the Hanafi Madhab.

Al-Salam alaykum
It is a condition for the validity of iqtida (following an Imam) in Fard salah that both the follower and the Imam be offering the same Fard salah. Hence one cannot offer `Isha’ behind an Imam offering Magrib nor can one offer Zuhr behind an Imam offering `Asr. In all these cases the salah must be repeated.
Abu Usamah