First off, welcome to the site!!!
The ZR5 package is an appearance package, the suspension and drivetrain are exactly the same as a normal crew cab. The ZR5 package adds different wheels, flares, bed rails, and a roof rack (might be some other stuff, but that's the main thing).
The ZR2 package is an off-road suspension package along with flares, skid plates, wider axles, and larger tires.
According to GM, these are the specs for the ZR2 package:
RPO ZR2 only full ladder-type frame with modified suspension mounting points which provide:
100mm wider track (3.9 inches wider than regular S-10)
Three-inch suspension height increase
Enhanced front (7.25" ring gear) and rear (8.5" ring gear) axles w/ 3.73:1 rear-axle ratio
Larger wheel and axle bearings
31 x 10.5R-15 LT/C black wall off-road tires (BFG A/Ts on pickups and BFG Long Trails on BlaZeR2)
46mm gas pressurized Bilstein Monotube shocks
Rear axle track bar (pickups) / rear sway bar (BlaZeR2)
Wheel flares (black on Chevrolet/body-color on GMC pickups)
33mm (early model) / 28mm (late model) front anti-sway bar
Skid plates (Aluminum through 1998 model year, carbon fiber thereafter).