You know, that's the argument that's always given when people don't know a better answer. God has the ability to feed us all with manna but are you going to stand out on your front lawn tomorrow morning and wait for it to fall? If you go to the grocery store, then you may very well be limiting God's ability to provide for you.
Nobody argues that God did not have the ability to create the universe in 6 days or milliseconds. The question is what did God CHOOSE to do.
You're basing your argument on one POSSIBLE interpretation of a single word in the early chapters of Genesis. However, the revelation that God gave us through his creation strongly contradicts that one possible interpretation. Why not choose the interpretation of that word, yom, that fits the evidence that God has shown us through his creation? You have two choices: (1) either your interpretation of the word yom is incorrect, or; (2) God's revelation through his creation is incorrect. Choose your pick.