I see a few ways to accomplish this.
1) with Inovelli smart switch and two auxiliary switches.
The inovelli dimmers can connect to a number of auxiliary (GE brand) switches. This gives some benefits:
a) because the aux switches connect directly to the dimmer there is virtually no delay in operation for any of the 3 devices.
b) you can dim from any location.
2) With dumb switches:
This is a typical 4-way showing how the "4 way" switch accomplishes the required function. There are a number of alternate wiring configurations for situations where the mains and lamp are in other location.
