1992 V-6 compression

Just recently purchased a 1992 4-runner V6. Engine shows zero compression in #3 and #6 cylinders (opposite sides). Upon putting oil in these cylinders and rechecking compression in these cylinders the reading still remained zero. The other cylinders showed readings of 155psi-160psi which according to the manual is passing. No steam is emitted from the exhaust upon driving. The vehicle is sluggish but there is no evidence of external leaking of antifreeze, no appartent water in the engine oil. The original owner took advantage of the dealer head gasket replacement (from reading the forums I now relize this is a historical problem). I was going to pressureize the cooling system and check for leaks however have not done this yet. I have no problem replaceing the head gasket set (Machine work) however I am looking for other input that would confirm this is a head gasket problem and not something in the small block section. Any input is appreciated....thanks

First thing I would suggest is a cylinder leakage test. Engine on TDC of compression and put regulated air into cylinder and see where it comes out(exhaust, intake, radiator or crankcase). My 0 compression was a burned exhaust valve.