The one with the "Discriminating Employer" on top of the tank? It's a little hard to explain, maybe moreso if you're not America, but I'll try. It's basically like this:
During WWII, the view in the USA was that everyone had to be firing on all cylinders because the chances of victory against the Nazis and various other fascists was a narrow one (the hourglass comic.) Everyone who wasted gas, spread rumors that might decrease the morale of the public, etc making it harder for the soldiers fighting the war and indirectly making them lose. It wasn't not just the average Joe, politicians, businessmen, and all sorts of people should be helping the war effort. Otherwise, the American war machine would just be all smoke and no firepower (big bertha comic showing how all sorts of vices make for a weak nation.)
Racism was one of these vices that Dr Seuss attacked. He saw various groups of people that weren't being used to their full potential because of prejudice, and if they weren't being used to their full potential, America was teetering that much closer to it's defeat against Hiter and the Japanese.
With the Discriminating Employer, you can see him on a big tank with lots of firepower, while the Negro and the Jew are stuck on tiny tanks with no guns at all, all at the behest of the Discriminating Employer. These "Jim Crow Tanks" refer to Jim Crow laws, which were laws or social mores that prevented blacks from becoming firemen, policemen, armed soldiers, or anything fan. They were usually stuck with shitty jobs like janitor.
Not only does this make the Negro and the Jew's role in the battle Discriminating Employer is driving to negligible, they're now a hindrance because they're attached to the big tank.
Dr Seuss's comic is saying it would be better if the Discriminating Employer were to not make the Negro and Jew ride the Jim Crow Laws (aka not screw them over by giving them shit jobs) so they can actively help him fight the bad guys.
tl:dr think of WWII as a tug of war game, and if you lose you die. Even if you don't like niggers, kikes, or whoever else, if they're willing to pull on your side, let them help.