Which of the following is NOT a special instruction when firing?

The correct answer is identified as "Cease loading." This phrase is often part of standard operating procedures related to the handling of ammunition and the readiness of the howitzer. It is a clear instruction that indicates when the crew should stop loading additional rounds into the weapon, which is vital for maintaining safety and operational control during artillery operations.

In contrast, the other terms represent specific firing conditions or commands that give necessary operational context for the crew's actions during firing. "High angle" refers to the trajectory of the projectile, typically used for indirect fire situations. "At my command" is a specific instruction that indicates firing will only occur upon a designated command, ensuring that crew members are synchronized and ready. "Sweep and zone" likely pertains to safety measures or specific targeting protocols during a fire mission.

Given the nature of the other options as direct operational commands or firing conditions, "Cease loading" is the one that does not fit as a special instruction related to the immediate firing context.