Yes, the leaves resemble hydrangea leaves. Probably a mophead or a lacecap. Try amending the soil with garden sulphur or aluminum sulfate; the leaves are turning yellow except for the leaf veins. That's called iron chlorosis.

Is there one main stem or several? I would hold off amending the soil for now or until you figure out what it is. Some hydrangeas are naturally lighter in color or on the yellow side. New leaves can be lighter and then change as they mature. It is a hydrangea for sure - but the type can not be determined at this time. I agree with Luis that is probably is a mophead or lacecap but that is about as far as you can guess - once it shows color then it will be easy to determine which of the two types it is, but correctly identifying the exact cultivar is very difficult because hydrangeas color and even size if variable depending on the soil and growing conditions.