When i engaged the blades it blows the fuse - Husqvarna Zero Turn Mower Z5426

SOURCE: 2007 Husqvarna Riding mower blade will not engage

Sounds like you electric blade clutch is bad. I just had the same thing happen to my exmark mower. I was cutting grass and the engine just shut down. It would not crank over. Checked the fuses and replaced one blown fuse. The engine wanted to crank over but it was locked up. I looked the engine over and seen that the bearing in the electric clutch seized up causing the clutch to melt.

Testimonial: "Thank you! That doesn't sound like an inexpensive solution. We appreciate your help, though."

SOURCE: When the blade engage knob

I started out on small engine so I'll try to answer this. Like most newer tractors, I'm sure it has an electric clutch that engages the drive belt for the mower deck. The clutch is under the engine on the end of the crank shaft, usually. It works like the a/c compressor clutch on a car. So a few easy things to check would be:
Is there anything jamming the blades or belt?
Is there anything jamming the clutch itself? (extra grass build up,etc)
If not, unplug the switch from the clutch harness & with a multi-meter set to read continuity or ohms, check the resistence to the clutch after the switch. If the meter "beeps" or goes high, the clutch is shorted & bad. Replace the blade clutch assembly.( not easy without the right tools) If it doesn't "beep" or reads near zero, the problem is the switch or a jam. Could be a chance that a wire shorted out in between the two as well. The seat switch can be eliminated because the engine runs. Try that.