Question Are those two memory modules compatible

Likely compatible; possibly not compatible.
Ram must be matched to work properly.
Even the exact same part number may be different inside.
I put your odds of success at 95% for intel processors, 85% for ryzen.

If you want 16gb and can not tolerate a no refund situation, I suggest you buy a 2 x 8gb kit with the same specs as what you own.
Try to add your old stick and perhaps you might get 24gb.
If it does not work, sell the old stick or keep it as a spare.

If you find that the ram does not work, your motherboard may be sophisticated enough to be able to increase the ram voltage from stock. That sometimes fixes compatibility issues.