Why does it say "Gedolim Ma'asei Hashem"?
Radak: This is the beginning of the thanks. What He did with the created beings, even though the deeds are great... (refer to 111:2:2:1).
Malbim: This begins to discuss three kinds of understanding in Hashem's conduct - Ma'asim, Pe'ulos and Nifla'os. Ma'aseh is something that is finished, that the worker need not engage in it more. Pe'ulah is something that the worker must engage in it more. Both of these apply to the creation. It was completed. However, Hashem is constantly renewing its creation. Sustaining the creation is like a new creation. Both of these are according to nature. There is also conduct that overrides nature - Nifla'os.
What is the meaning of "Derushim l'Chol Cheftzeihem"?
Radak: Anyone who wants to contemplate [His deeds] and seek them, they are available. Cheftzeihem is To'ar (adjective), from Chafetz/ Chafatzim, just like Zaken/ Zekenim/ Zikneihem.
Malbim: Every action has a Chefetz, i.e. purpose. One builds a house to live in it, a chair to sit on it... Hashem did not create the world for His need, rather, for the deed (creation) itself. He made [natural laws] to fulfill all needs of the creation. One law can supply several needs - spreading of air causes rising of vapors to make clouds, blowing of wind, sprouting of vegetation...
