Not sure if it is only me, but on mobile I can’t zoom into pictures others post.
I can click on them in a thread and they open in an overlay kind of view where I can download the picture etc., but pinching with 2 fingers (the movement you do to zoom into things) doesn’t do anything.
This makes it kinda impossible to read labels or similar on mobile. But maybe I do something wrong? 
No idea but it works for me (checked now). I’m using chrome web version of the forum. If you still struggle, my brute force recommendation is to open image in new tab.
Played a bit more around with it, if I open the forum separately in a browser I can zoom without issues.
Seems to be more in combination with the integration into the app that the zooming gets a bit fickly, the app always tries to switch over to the „Splits“ section instead.
So probably more an issue with my fat fingers instead of the forum 