You are asking for a software which can be used to zoom mp4 videos so that you can find the robber's face from the recorded video. The answer to your question depends on the resolution of mp4 video recorded by the camera. If it is in 1080p resolution or higher, you can get a glimpse of the robber's face. But if the video is in lower resolutions, the face is pixellated (blurred) as the video is zoomed.
Cyberlink Player is a video player I know which can be used to zoom videos while playing. If a video player does not have that feature, you can just take a screenshot (almost all video players have this feature) and zoom it using any picture viewer. So, you can be sure that videos recorded in higher resolutions can only be zoomed to get the proper details.
Hope this answer helps.