Zone of truth would affect undead, but the corpse is not undead. But Speak with dead does not create an undead. It does allow the corpse to speak what it knew in life. Additionally, Speak with dead spell text says

Answers are brief, cryptic, or repetitive, especially if the creature would have opposed you in life.

If the dead creature's alignment was different from yours, the corpse gets a Will save to resist the spell as if it were alive. If successful, the corpse can refuse to answer your questions or attempt to deceive you, using Bluff. The soul can only speak about what it knew in life.

So the orc corpse might not lie but it probably won't give a straight answer, either. Unless it saves, then it can absolutely lie -- but then Cleric Bob gets a Sense Motive check to tell if the corpse is lying.

Zone of truth would not affect the corpse, no.   Speak with dead does not create a creature from the corpse. It does allow the corpse to speak what it knew in life. Additionally, Speak with dead spell text says

Answers are brief, cryptic, or repetitive, especially if the creature would have opposed you in life.

If the dead creature's alignment was different from yours, the corpse gets a Will save to resist the spell as if it were alive. If successful, the corpse can refuse to answer your questions or attempt to deceive you, using Bluff. The soul can only speak about what it knew in life.

So the orc corpse might not lie but it probably won't give a straight answer, either. Unless it saves, then it can absolutely lie -- but then Cleric Bob gets a Sense Motive check to tell if the corpse is lying.