To check the hydraulic fluid on a Husqvarna zero turn mower, follow these steps: 1. Park the mower on a level surface and turn off the engine. 2. Locate the hydraulic fluid reservoir, typically located near the rear of the mower. 3. Remove the cap from the reservoir. 4. Check the fluid level visually; it should be between the minimum and maximum markings on the dipstick or sight glass. 5. If the level is low, gradually add the recommended hydraulic fluid, avoiding overfilling. 6. Securely reattach the cap and ensure it is tightly sealed. 7. Start the mower and test its functionality.