Tap any image to open full-screen. Pinch to zoom on mobile, scroll-wheel on desktop. Drag to pan. This is the e-commerce standard (Zara, Net-a-Porter, Farfetch all use this pattern).
Hover (desktop) or tap-and-hold (mobile) to reveal a magnifying glass that shows 3x detail. No full-screen needed. Works inline on the page.
Two panels side by side. Left shows the full image, right shows a zoomed-in crop that follows your cursor/finger. Lets the visitor see context and detail simultaneously.
End of prototype. Which approach works best?