Zach often reminds me of helpless wasps on a hot summer day. Like a poor insect, he unknowingly gets trapped inside the house. He keeps pounding against the closed window not realizing that the window above him is completely open.
A comma is indeed missing here, the correct version would look like this:
Zach often reminds me of helpless wasps on a hot summer day. Like a poor insect, he unknowingly gets trapped inside the house. He keeps pounding against the closed window not realizing, that the window above him is completely open.
Zach often reminds me of helpless wasps on a hot summer day. Like a poor insect, he unknowingly gets trapped inside the house. He keeps pounding against the closed window, not realizing that the window above him is completely open.
Zach often reminds me of helpless wasps on a hot summer day. Like a poor insect, he unknowingly gets trapped inside the house. He keeps pounding against the closed window, not realizing, that the window above him is completely open.