The only laws we need in this instance are the provisions in the U.S. Constitution which set forth the impeachment process.
After much debate, the Founders settled on "treason, bribery, and other high crimes and misdemeanors" as being possible grounds for impeachment. Most scholars agree that the definition of "high crimes and misdemeanors" is a flexible and fluid one, and the power to decide what it means ultimately resides in Congress.
If I were a Congressperson, the transcript of the Zelensky phone call alone (which speaks for itself) is all I would need to cast my vote in favor of impeachment. Since we're talking about Trump here, there are of course dozens of other violations to choose from from emoluments clauses violations, to obstruction, to denigration of the democratic process, to other instances of abuse of office.