One of my friends has a Hitec Prism 7-channel Tx. He is going to buy my Eclipse 7 QPCM.

The Prism module is marked "HPF-M".
The Eclipse module is marked "HPF-Mi".

Are these modules compatible? Can he use the module from the Prism in the Eclipse?

We'll have to look into the specific part numbers. Generally speaking the modules are interchangeable from TX to TX. Specific frequency or bands must be adhered to in your location.

We tried.

It works.