The concept of "Zero Hour" in the Indian Parliamentary process refers to the time between the Question Hour and the next item on the agenda. During this period, Members of Parliament have the opportunity to raise important matters which require immediate attention and cannot wait for the regular proceedings.

Option 1: The intervening time between two different items on the agenda is not referred to as the Zero Hour. It is simply the time gap between different agenda items.

Option 2: This statement is correct. The Zero Hour is the time immediately following the Question Hour and before the next item on the agenda. It provides MPs with the chance to discuss urgent issues.

Option 3: The time immediately after the Question Hour is indeed a part of the Zero Hour, but there is no mention of it being extended for more question-answer sessions at the Speaker`s discretion. This option is not entirely accurate.

Option 4: This option is incorrect as the correct answer is stated in option 2.

In summary, the Zero Hour in the Indian Parliamentary process is the time between the Question Hour and the next item on the agenda, where MPs can raise urgent matters for discussion.