Zoom lens and image pickup apparatus having zoom lens

A zoom lens comprising, in order from an object side to an image side:

• a first lens unit having positive refractive power;
• a second lens unit having negative refractive power;
• a third lens unit having positive refractive power, the third lens unit having, in order from the object side to the image side, a first positive lens, a first negative lens, and a second negative lens;
• and
• a fourth lens unit having positive refractive power,
• wherein the zoom lens performs zooming by changing the distance between the lens units, and
• wherein the zoom lens satisfies the following conditions:
• 0.20<Da3/TD3<0.35
• 0.3<f3/f4<1.0
• where f3 is the focal length of the third lens unit, f4 is the focal length of the fourth lens unit, TD3 is the distance between the surface closest to the object side and the surface closest to the image side in the third lens unit, and Da3 is the distance between the surface of the first positive lens facing the image side and the surface of the first negative lens facing the object side.