No compression

You have no compression on all cylinders? If this is the case then we are missing something because if the rockers are moving, one would assume the cam is turning and the dowel pin is not sheared. However, unless you lost the compression ring on all cylinders then you have a valve issue or head gasket issue on both sides.

The fact that this is unlikely I would remove the timing gear and make sure the alignment pin or dowel pin is not sheared. Basically we have to find why we have not compression on all cylinders and that has to be something that is in common for all cylinders.

I suspect this is not all cylinders because you said it ran poorly and if you have no compression on all cylinders then it would not start. If this is the case, which cylinders do you not have compression on? The way to tell where the leak is of compression is to do a leakage test. Let me know if you have down this and where the air is escaping.

Keep us updated with what you find and if you need more assistance. Thanks