Oil in the cyl is good if you have low compression and want to find out why.

To get zero compression and have it be the piston / rings , you would have to have a hole in the piston. Two pistons with holes, side by side seems unlikely. Pistons with holes dont change from putting oil in the chamber.

Pressurizing the cylinder will tell a lot.....

A couple of bad jet valves could do the same. It's the side by side failure that usually says head gasket.

The upside is jet valves can be changed without pulling the head, worth checking. Anything other than that , and the head has to come off.

Kevin