How to read in continuum Verse 99 of Sura al An'aam (6)?

Assalamu alaykum wa rahmatullah

Question: about linking tanween and hamzatul al wasl

How to read in continuum Verse 99 of Sura al An'aam (6)?

In similar cases, I know that we use an addition nuun. I also know that the noon should have kasrah in some cases. The question is to know whether the noon should have kasrah in all cases, no matter what the vowel of the third letter is, or if it should have dammah if the third letter of has dammah (like the third letter rule for starting the reading on hamzatul wasl).

Therefore, if (just if) we want to continue the reading between the tanween of "mutashaabihin" and "unthuruu" is it

“mutashaabihi-nin-thuruu”  or    “mutashaabihin-nun-thuruu”
(nuun with kasrah)                     (nuun with dammah)?

Your help will be highly valued. I have been suffering from this question for a long time. Your correct, clear and prompt answer will be a real deliverance. And I wish for you an appropriate reward: deliverance from all your difficulties in this life and jannah alfirdaws.

Wassalam wa rahmatullah.

Wa alaikum assalaam wa rahmatullahi wa barakaatuh
In aayah 99 of surah al-An'3aam, we have the phrase .  If we do not stop on the first word and instead read them together, we have then two saakin letters meeting: the first the noon saakin of the tanween, and the second the noon saakinah in the second word.  We ignore the hamzah wasl when joining the two words.
In the recitation of Hafs 'an 'Aasim, we always put a kasrah on the noon saakinah of the tanween when two saakin letters meet.
We would therefore read it as: , with a kasrah on the ha' and the noon saakinah of the tanween also with a kasrah.
As we stated, this is for Hafs.  There are other qira'aat who would put a dhamm and the noon saakinah of the tanween because it is followed by a verb and the third letter of the verb has an original dhammah. 

May Allah give you all khair.  Jazakum Allahu khairan for your kind dua'.  Ameen, and may you be rewarded with the same.
Wa assalaam alaikum wa rahmatullahi wa barakaatuh