I did not have the described problem in Parallels 8 This started with the installation of Parallels 9.
I have a Windows 7 64bit VM. One of the programs has several windows with images. I used to be able to use my trackpad placing two fingers on it moving up or down to enlarge or reduce the images. Like a center scroll wheel on a Windows mouse. This no longer functions with Parallels 9. I have looked for configuration windows to make sure something didn't get turned off or re-assigned. I can find nothing to help.
Is this a bug in Parallels 9? Is there a fix or work-around? If not, is there a site where I can downgrade to Parallels 8? I have to have this function.
Edit - Never mind. I see you added the Mac pinch and zoom gestures. VERY NICE.