Hi,
in every single app but Thunar when you hold Ctrl and scroll the mouse wheel the size of content grows with scrolling up.

Steps to reproduce:
1. Open Thunar
2. Hold Ctrl and scroll the mouse wheel up

Actual result:
Icons become smaller.

Expected result:
Icons become bigger.

Vice versa:

Steps to reproduce:
1. Open Thunar
2. Hold Ctrl and scroll the mouse wheel down

Actual result:
Icons become bigger.

Expected result:
Icons become smaller.