Tips and tricks for playing Heroes 3.

What is the main feature? Harpies (improved!!) have high speed and retaliatory strike. Therefore, you only need to inflict retaliatory strikes on golems, while using them to fly away from the slow-moving golems on the map.
This tactic works not only with harpies, but also with any monsters with retaliatory strike and good speed against slow-moving units. (For example, fairies against zombies, etc.)

P.S. As a variation of this tactic, use walking monsters against fast monsters to "flee" and distract attention, along with a siege unit with ammunition (or a ballista).