The iPadOS Zoom feature utilizes three-finger gesturing to zoom into applications. This competes with ZBrush's three-finger gesture used for adjusting Draw Size.
Disable the iPadOS Zoom feature.
When disabled, three-finger gestures should take effect and function normally.
iPadOS Settings > Accessibility > Zoom
ZBrush performance is known to lag in M4 processor iPads due to software conflicts between iPadOS settings.
Enable iPadOS Low Battery mode.
ZBrush for iPad functions the same as the desktop version. For technical support, release notes, FAQs, and more, visit the Maxon Knowledge Base.