How to improve this user interface design?

I create a small calculation tool to calculate the monthly payment needed to reach an end goal or to calculate the end goal based on a monthly payment. I created this using two tabs so that users could switch between these two calculations.

But now another requirement has come to also change the calculation and the labels depending on whether it is a new loan or a loan transfer. existing. My first instinct was to create it like this: https://jsfiddle.net/r4kmgvz2/. But I think there must be a more intuitive way to design the user interface for this concept.

I first created this tool with Python in Tkinter, and I now redraw it in Vue.

(Note: What is the best title for this question?)