Double tap to zoom on Pixel 3a chrome browser?

Since Chrome 32, Google started removing the 300ms to allow the double tap to zoom in or out for mobile sites.

For many years, mobile browsers applied a 300-350ms delay between touchend and click while they waited to see if this was going to be a double-tap or not, since double-tap was a gesture to zoom into text.

Ever since the first release of Chrome for Android, this delay was removed if pinch-zoom was also disabled. However, pinch zoom is an important accessibility feature. As of Chrome 32 (back in 2014) this delay is gone for mobile-optimized sites, without removing pinch-zooming! Firefox and IE/Edge did the same shortly afterwards, and in March 2016 a similar fix landed in iOS 9.3.

According to Google:

Is losing double-tap-to-zoom an accessibility concern?

No. Pinch zoom continues to work, and OS features cater for users who find this gesture difficult. On Android, magnification gestures takes care of it. Tools like this even work outside the browser.

However, if you request desktop sites, you will still be able to zoom in/out off pages using the double tab. For mobile sites, you should enable Magnification gestures and use the triple-tap to zoom.