I hope I can help, but I have to admit I am a total newbie at working with API calls.

What I wound up doing was setting up the first call as one workflow action run on an image input (I named the call TinyPNG_Shrink as shown here, and then the second call as a second workflow action (I named TinyPNG_Resize) to run on the result of the previous action.

I used the TinyPNG documentation to construct the JSON Body (and I think I had to make the second call a Data type of Image rather than JSON for some reason.)

chrome_1ZkjQWPtzl

I can’t remember where I got the initial value for the ID in the call, but IIRC that goes into the ID field of the second call in the workflows here.

chrome_MhmSwwJJMM