Parallel Z phasor diagram!

In order to draw a phasor diagram showing Z and R and Xc in a parallel circuit, we need to first convert that parallel circuit into an equivalent series circuit.  In our textbook, Floyd 8th Edition of Electronics Fundamentals p. 478 in the RC chapter we find the answer. (I have shown the book pages here as larger unclear thumbnails just for reference, please refer to your textbook to read and understand it)