AI saw a video of the Skype CEO, scream toing about Zoom because most market share is been takenit's taken most of his market share away!

Is this what you mean? The original sentence didn't seem to make much sense, it felt more like a fragment than a subject-verb-object main sentence.

This video is so fun to watch, but at the same time I can feel his pain.

Or "you can feel his pain" if you want to say that any person watching could feel it.

I am've been a sSkype user for a long time, even now I am still using it.

I think it will often sound strange to use simple present tense or present progressive tense with a duration like "for a long time". A duration is going to extend into the past or the future, usually - the present is a moment, an instant, and it's hard to fit a duration into it. The only way I can think of that this would be natural is if you were narrating the actions of a story in present tense. "Imagine: I'm in my car. I'm driving to work. I'm driving for a long time. Suddenly, I am abducted by aliens!"

Literally any other tense would work but present perfect seems (as so often) most appropriate in this particular sentence.

"I still using" has no finite verb. You could say "I still use it", or you could use the participle like you have - but then you need "am" to serve as your finite verb: "I am still using it".

But underin this pandemic situation most people just choicose zZoom.

"choice" is a noun.

"under" might be okay here, I'm not sure. But "in" is definitely more natural.

If I amwas the CEO of Skype and I was watching how zZoom growthew so big within such a short amount of time.,

When we construct a conditional sentence, we use past tense to mark something as being counterfactual, impossible or unlikely. "If it is raining, he'll be outside" - it may or may not be raining, both are possible. "If it was raining, he'd be outside" - it's not raining, but I want to tell you where he would be in the non-existent, imaginary scenario where it is raining.

Here, I think we can safely assume that you being the CEO of Skype is not a realistic possibility :)

In the second part of the sentence you again have missing verbs. "growth" is a noun but we can use "grew", or we could pair "growth" with a verb like "how Zoom's growth exploded within..."

And I join this sentence with the next because a conditional sentence without a consequent is not really grammatical. "If" and "then" should be in the same sentence.

I willould be more angry thean him!

"would" instead of "will" is conditional sentence grammar again.

And you need a copular verb to use "angry" like this. I am angry, he is angry, they look angry, we will get angry, I will be angry, I would be angry. I think this applies to all adjectives. Here you had no copular verb.

But still no one can answer this question, why zoom isis Zoom better than skype?

Just question word order :)