Fan speed control on Zyxel switch?

Thank you for the images, they are helpful. It looks like I have the V1.

Fortunately, I was able to rewire the fan header on the new fan and make it match the OEM fan. It works perfectly and is much quieter. 

I don't think fanless is a good idea after seeing the inside of my switch. There is a heatsink that gets pretty toasty to the touch
(it won't burn or anything but it's uncomfortable after a few seconds)

I don't know the OEM fan specs, but it doesn't seem to matter all that much to the switch. It'll operate with or without a fan and has no way of telling apart one fan from another. The RPMs are not listed on the fan or in the software, so I can't say I have a matching fan but it's certainly quieter. (didn't require any mods either besides correct wiring)

For owners of the V1, a quieter fan is about $7 and 10 screws. Fanless is not a good idea unless you have other airflow to offer such as leaving the switch open with maybe a 120mm fan (120s are very quiet) pointed at it. This thing NEEDS some kind of airflow to maintain performance.