The 55 V Vdss rating gives 20% derating margin on a 48 V nominal bus, which is the usual practice for telecom rectifiers and e-bike battery circuits. The 30 A continuous current at case temperature 25°C derates with case heating — at 100°C case you typically lose about 40% of that figure, so size the thermal path accordingly. Gate drive flexibility is a design convenience: the IRLZ34NS specifies both 4 V and 10 V drive voltages for achieving the stated Rds(on). With a 25 nC typical gate charge at 5 V, a microcontroller GPIO driving through a small gate resistor can switch it fast enough for 20-50 kHz PWM without a dedicated gate driver IC.
Infineon has ended production of this exact order code. New stock is no longer flowing through the factory, so any units available today are from distributor inventory or surplus channels. The IRFZ34NS or similar active-series parts offer a pin-compatible footprint with updated silicon.