If an object travels at a constant velocity indefinitely, does that mean the resultant force is zero?
The terminology “resultant force” in your question is peculiar. “Resultant” is usually used when a force is the result of other forces. Your question sounds like it means: “What net force must be exerted on a body to keep it in motion with a constant velocity (for an arbitrarily long time)”. The answer to that is zero force, which is also a constant force.
