Your Eevee-targeted 3D model lags in ZBrush mainly due to high polygon counts, excessive subdivision levels, or unoptimized geometry (like overlapping faces).
ZBrush’s viewport prioritizes real-time sculpting—heavy geometry (e.g., millions of polygons) forces it to process more data at once, slowing display.
To reduce lag: Temporarily lower subdivision levels (press Shift+D), merge overlapping vertices, or use ZBrush’s “Decimate Master” to simplify the model while keeping key details during work.