Extortion

The Democrats are accusing the President of extortion.  It may help to understand what the word "extortion" actually means in the legal sense.

Here is a webpage that discusses the elements of extortion.   Most of the discussion was about the acquisition of money or property of another person by force or fraud.

Nothing in this article applies to the President.  In order to be guilty of extortion, one has to force something from someone that they would not give willingly.  A mere exchange of favors ( quid pro quo ) is not extortion.  Withholding military aid is not a threat to do harm.  The refusal of help is not a threat.  The harm is coming from Russia, not the USA.  Trump wasn't threatening the Ukrainians.  It is a big stretch to say that he was.

Zelensky could have given the President a statement willingly with no strings attached.  The aid question is coincidental as it wasn't necessary to Trump's request.  Each could be separate issues entirely.

Even if you accept that these elements do apply to Trump, you still have to prove them.  The Democrats haven't even done that.