See https://www.ec-gearing.com/. I'm wondering if it's possible to CNC machine / mill this at all with very high accuracy.
I have seen videos, and one instance in person, of a multi-axis CNC machining center performing quite complex milling/machining in which the work piece is rotated simultaneously with the tool head. These machining centers can produce work with tolerance of one tenth of one thousandth of an inch.
The difficult part of such a construct is creating the g-code necessary to produce the desired part.
As your title asks, can this be done with conventional methods is more dependent on what you consider conventional. A multi-axis machining center is conventional in that it does not involve additive manufacturing, laser cutting or other somewhat esoteric processes.
There was a successful Kickstarter campaign known as Pocket CNC, a rather compact 5-axis milling machine. I'm not versed in the accuracy/precision of the device, but it also falls back on the ability to generate g-code to make the required parts. I've noted just now that the mill is limited to materials up to the hardness of aluminum.
Image from Kickstarter campaign.
Piece of cake with single point CNC. When I retired years ago very complex threads were being cut on oilfields tubulars. Look up the Hydril wedge thread series of connections: not possible to describe in a reasonable amount of words. These threads may be cut on high strength steel ( 140,000 psi tensile). For a gear they would likely be surface carburized after machining.