If you zoom out the game tries to draw more tiles. The more tiles the game tries to draw, the laggier it gets, because Terraria isn't optimized.

Go to Better Zooms Mod config.
Change the setting "Tile Render Limit" to a lower value. If you set it to 1, the game shouldn't draw any more tiles and the lag should be gone.

If for some reason it still lags, you can try to set the setting "render more tiles" to off. After a reload, the mod won't try to draw any more tiles (like in pevious versions).