Wiring for a generator Inlet and EV charger
UF-B in conduit is a nightmare.
You can't fit even one 6/3 UF-B into a 1-1/2&quot; conduit.
One 6/3 UF cable requires 2&quot; conduit.
Two 6/3 UF cables require 3-1/2&quot; conduit!
Since 3-1/2&quot; conduit is required, 1-1/2&quot; conduit is right out :)
Your only option is to have a junction box at each end of the conduit run, and splice from UF to THHN wire for the run  inside the conduit.  Note that your junction box will require 65 cubic inches because you'll have 12 active conductors being spliced all in all, plus 4 grounds (which count as 1/4 wire, rounding up). Each #6 wire requires 5 cubic inches.   Eight THHN wires will fit very comfortably inside a 1-1/2&quot; conduit.
Note with #6 THHN, neutral must be on a white or gray wire, and ground must be green or bare - no remarking wires with tape.