What is the different between these two RegEx patterns

Why does this regex return null:

"abcabc1Z".match(/^(?=w{3,6})(?=.*d)(?=.*Z)$/)

That returns null but this:

"abcabc1Z".match(/^(?=w{3,6})(?=.*d)(?=.*Z)/)

does not return null (the difference the second pattern does not include $).

Why does the first one return null? Shouldn’t both return the matched string?