Simple.
The INTJ should use active listening skills to make the INFJ feel heard and validated, and consciously resist the urge to dismiss things they disagree with – their goal in the interaction to achieve empathy and understand the position of the INFJ in order to negotiate an optimal outcome which benefits them both. INTJ should take care to avoid phrases which could be interpreted as direct criticisms or judgement of the INFJ.
The INFJ should resist the urge to become defensive, and hear the words the INTJ is using without reading into it for hidden emotion or motivations. The calmer and less visibly emotional the INFJ can be, the better. Use clear examples, don’t generalise, stick to one issue per conversation (if it’s emotional) and come to the conversation with satisfactory positive outcomes predetermined. The correct emotions the INTJ is feeling will be clear from their word choice, they’re direct even though they’re reserved. The INTJ wants to avoid awkward emotional displays and maximise utility of their time.
Both types are very rational and goal-focused, capable people who like calm. INFJ needs to ask directly for what they want, don’t hint, and be prepared to explain their reasoning. INTJ needs to prioritise the INFJ, allow them time, and give their full attention for that conversation. Both types will likely compromise and both are very honest sorts of people.