In the Mishnah of Masechet Taanit we have the following:
(4:6) Five things happened to our fathers on the 17th of Tamuz, and 5 on the 9th of Av. On the 17th of Tamuz:
- The tablets were broken
- The Tamid offering was ceased
- The walls of the city were breached
- Apastumus burned the Torah
- And he put up an image in the Heichal
On the 9th of Av:
- Our fathers were sentenced to not enter the Land
- The First Beit HaMikdash was destroyed
- And the Second (Beit HaMikdash was destroyed)
- Beitar was captured
- The city (Yerushalayim) was plowed
I would like to examine just the underlined items in blue shown above, regarding the walls of Yerushalayim and the Tamid offering.
The Zohar Chadash says that from the time of the cessation of the Tamid to the destruction, for both of the Batei Mikdash was 22 days. Note that it is 22 days and not 21 days; this is connected to the drash in Mechirat Yosef where this statement is made, where 22 is related to the 22 years that Yosef didn't see Yaacov.
The Talmud Yerushalmi (4:5) comments on both events separately. Regarding the Tamid, it recounts how during the sieges on Yerushalayim, the Jews used to send money out over the city walls in exchange for animals for the korbanot, and then one time the Romans sent up 2 pigs. It then goes on to say from that time, the sins caused the Tamid to cease and the Beit HaMikdash to be destroyed. See there for the entire account, which is also recounted in Yerushalmi Brachot. The next section of the Gemara is already dealing with the breach of the walls. The section regarding the breaching of the walls has to do with the actual dating of the events, because of the difficulty regarding the dates we go by and the dates which appear in the Tanach. The Yerushalmi states that the dates that are recorded in the Tanach are wrong, and were incorrect due to the troubles occuring at the time. See the mefarshim there on the daf for more.
The Bavli (Tannit 28b) is even more terse regarding the Tamid. It has one word: Gemara. Rashi there says "thus we have received from our fathers". I.e. it is a tradition that it occured on this day. On the breach of the walls, the Bavli says that it is not a problem, 17th of Tamuz is only for the 2nd Beit HaMikdash, the other date, namely the 9th of Tamuz, was for the 1st Beit HaMikdash. The Yerushalmi also brings this as a secondary explanation aside from the one I mentioned above.
As we can see from the two Talmuds, there is no explicit saying that the Tamid offering ceased the same year that the Beit HaMikdash was destroyed. The closest statement is the line from the Yerushalmi that in that hour, the sins caused the cessation of the Tamid and the Beit HaMikdash to be destroyed. However, just as all that was not in "that hour", so too not necessarily in that year.
The Zohar Chadash on Mechirat Yosef, however, is more of a problem. It says 22 days difference, and it links it to the Tamid, not the breach of the walls. However, I think the important item for this drash is that it is 22 days apart on the calendar, not necessarily that it is the same year. I have reason to believe, because of elsewhere in the Zohar, that this is the case, and that there is no contradiction.
From this we see the source of the different traditions regarding when the cessation of the Tamid offering took place. For some the different possibilities, see Mikraot Gedolot on Daniel. I do not believe, however, that the answer is to be found in the Mikraot Gedolot. HaMevin Yavin.