Merriam Webster dictionary's phonetic transcription is /dɪ-'zi:z/. But in this movie trailer: The Thinning 2016, min 0:13 'What causes disease', it sounds like /dɪ-'zi:s/. I believe i hear the hiss sound at the end. So which one is correct? which way should i go with? Thanks.
The phoneme here is /z/, just as you'd expect based on the transcription available in a dictionary. That is to say, native speakers of English will definitely hear this sound as /z/.
However, you're quite right that you're hearing an [s] sound! The /z/ sound here has undergone a phonetic process known as devoicing, something native speakers generally don't notice (as you can see from the comments section on your question). With devoicing, the /z/ phoneme in this word is actually pronounced as [s].
In fact, it takes special training to be able to hear this, as this distinction is non-phonemic in English, and native speakers spend their whole lives training to ignore non-phonemic distinctions. You can hear it because you're a non-native speaker, so you haven't trained your whole life to ignore it.
I am a native speaker, and I hear a /z/ in this recording as well. And yet, if I isolate just the /z/ sound, removing all of the other sounds before and after it, I hear an /s/ instead! So yes, most of the /z/ sound has been devoiced in this example, and your ears are working properly. It's simply a matter of how our brains interpret the sounds we hear being different.
In this case, /z/ is devoiced because it's in utterance-final position. For a full explanation of when this sort of devoicing occurs, please read Araucaria's post on English Language & Usage.
As Araucaria explains in his answer, you do not need to try to devoice the /z/ in this sound when you say it yourself. Native speakers do it, but they generally can't hear it, so there's no reason to try to do it yourself.
When you pronounce this word, pronounce it as the dictionary suggests, with a [z] sound.