You are missing the point - the OP is not using an LTE device, the Raspberry Pi Zero can present itself as an RNDIS interface which the Mikrotik is assuming to be an LTE modem instead of an ethernet adapter.
Unfortunately there is no documentation as to how Mikrotik enumerate USB devices, certainly they support some USB - Ethernet dongles. It may be a case of just having to change the vendor & device ID presented, or the type of device.
Well worded. Exactly what I am trying to accomplish. Right now I have this vendor and product id:
options g_ether idVendor=0x05ac idProduct=0x1402 iProduct=Pi0 iManufacturer=Raspberry
Found this in another topic here that this one works with mikrotik. It's some apple device. I could try some other device ids, but I am unsure which are supported by mikrotik. Is there a list of vendor ids/product ids that are recognized by mikrotik as rndis compatible devices? Or even usb-ethernet ones. But I am unsure whether the latter would even work.