Take The Data to The User

I am working on integrating with a large system. This is one of those applications that my users spend half their time using,

There are two main approaches to integrating with systems like that.
One is to extract the data and present it inside the system you have. This means that the users have to use both the system they are using and yours.

The second approach is to push your data into that large system. There are several ways of doing this.
Embed a custom UI inside the system (if it allows for that). Another alternative is to use some form of commenting system as a UI. If you can write an HTML table then you can embed whatever data you need in the UI, This will be challenging but very rewarding for the users as they won’t have to switch away from their primary system.