Uh ...
Pz III maxed out with the 50mm/L60 cannon (or the 75mm/L24 in the ausf. N ... but that's more of a close support howie). The T34 completely outclassed the Pz III during the war, and the Pz IV up til the ausf. F2 came out, at which point the Germans at least had stand-off firepower, but were down on armor and manouever potential.
A Pz. IIIj would kind of be a match for a M4A1 Sherman since the US 75mm wasn't that great. But neither could compete with the Pz IVh in firepower or the T34 in armor/speed.
(... the scary thing is I remember all this stuff still ...)
Besides, we already have 3 German armored vehicles.