How to zoom .psd with vector graphics in AE without losing quality?
Using Photoshop to create vector graphics is a bad idea, as it is just not built for that. Even if you don't use the more sophisticated features of Illustrator, the basic tools such as the pen work somewhat similar to the vector tools in Photoshop. So next time you want to create vector graphics, just work with Illustrator from the start. 

For your existing vector graphics, as long as they are truly vector-based in the .psd-files, there should be several ways to export them to a vector format or copy them over to Illustrator (this doesn't directly answer your question, but it's a better approach than trying to make the .psd files work with vector graphics within After Effects anyway). Here are two options for you to try:


Export as svg [requires Photoshop CC]. In Photoshop, use File → Export → Export as.... Select SVG from the dropdown menu. SVG is an XML-based vector format. You should be able to import those into After Effects directly. Or you can open the exported SVG file in Illustrator and export it to another format.
Open your .psd file in Illustrator. Chose 'convert layers to objects' in the Photoshop import options. As long as your .psd contains only vector objects, this will work as intented. Once you have imported your vector graphic to Illustrator, save it as an .ai file. You should be able to import that into After Effects to work as intended. If that doesn't work for some reason, try saving it as an .eps file instead (File → Save a copy... → Select Illustrator EPS from the dropdown menu in the file saving options).