if I do not know which type url ZF using now, how to rebuid the request url when I want to chang or add some params?

Example:
ZF now url is "/abc/list/a2/3333",
I want to add a "a1=222222" to request url or change "a2=3333" to "a2=4444",
then how to rebuild url to "/abc/list/a2/4444/a1/222222",
if ZF now url is "/index.php?abc/list/a2/3333",how to rebuild url to "/index.php?abc/list/a2/4444/a1/222222"

I want a ZF method! Thx!